math 124: lecture for week 4 of 17online.sfsu.edu/meredith/statistics/s2008/lecture_4_slides.pdfweek...
TRANSCRIPT
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Math 124: Lecture for Week 4 of 17
David MeredithDepartment of Mathematics
San Francisco State University
February 19, 2008
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Class progress
• As of 5:30PM• only 10 people had completed the Lab Exercise• only 4 people had read the complete assignment
• Passing this class is up to you.• If you do the work, you will get a good grade• An hour a day, every day, is what you need to do
• Do two 30-minute sessions if that works better
• First on-line quiz due Thursday, second on-line quizdue one week from Thursday.
• First midterm in two weeks
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
What we will do tonight
1 Questions and Answers
2 Quiz
3 ReviewStandard DeviationReview Case IReview Case IIReview Case III
4 Sampling
5 Designing StudiesObservational StudiesExperimental StudiesSurveys
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
What we will do tonight
1 Questions and Answers
2 Quiz
3 ReviewStandard DeviationReview Case IReview Case IIReview Case III
4 Sampling
5 Designing StudiesObservational StudiesExperimental StudiesSurveys
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
What we will do tonight
1 Questions and Answers
2 Quiz
3 ReviewStandard DeviationReview Case IReview Case IIReview Case III
4 Sampling
5 Designing StudiesObservational StudiesExperimental StudiesSurveys
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
What we will do tonight
1 Questions and Answers
2 Quiz
3 ReviewStandard DeviationReview Case IReview Case IIReview Case III
4 Sampling
5 Designing StudiesObservational StudiesExperimental StudiesSurveys
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
What we will do tonight
1 Questions and Answers
2 Quiz
3 ReviewStandard DeviationReview Case IReview Case IIReview Case III
4 Sampling
5 Designing StudiesObservational StudiesExperimental StudiesSurveys
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Questions and Answers
•
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Go over quiz
www.cmu.edu/oli
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Apply the standard deviation rule
Question 1:
• Calculate the mean and standard deviation of thedataset:
5.1 6.4 6.5 8.8 8.8 9.4 9.9 10.110.2 13.1 13.5 13.5 13.6 14.4 14.6
• Is this data approximately normally distributed?• Implicit understanding for this class• Whenever you get a question like the one above, the
answer isn’t just “yes” or “no”; the answer is “yes,because . . . ” or “no, because . . . ”.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Apply the standard deviation rule
Question 1:
• Calculate the mean and standard deviation of thedataset:
5.1 6.4 6.5 8.8 8.8 9.4 9.9 10.110.2 13.1 13.5 13.5 13.6 14.4 14.6
• Is this data approximately normally distributed?
• Implicit understanding for this class• Whenever you get a question like the one above, the
answer isn’t just “yes” or “no”; the answer is “yes,because . . . ” or “no, because . . . ”.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Apply the standard deviation rule
Question 1:
• Calculate the mean and standard deviation of thedataset:
5.1 6.4 6.5 8.8 8.8 9.4 9.9 10.110.2 13.1 13.5 13.5 13.6 14.4 14.6
• Is this data approximately normally distributed?• Implicit understanding for this class
• Whenever you get a question like the one above, theanswer isn’t just “yes” or “no”; the answer is “yes,because . . . ” or “no, because . . . ”.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Apply the standard deviation rule
Question 1:
• Calculate the mean and standard deviation of thedataset:
5.1 6.4 6.5 8.8 8.8 9.4 9.9 10.110.2 13.1 13.5 13.5 13.6 14.4 14.6
• Is this data approximately normally distributed?• Implicit understanding for this class• Whenever you get a question like the one above, the
answer isn’t just “yes” or “no”; the answer is “yes,because . . . ” or “no, because . . . ”.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Compare and contrast distributions of quantitative data from
two or more groups
Question 2: here are scores from a test I gave to Math 124last semester.
100 100 92 92 83 83 83 83 75Women 75 67 67 67 58 58 58 50 50
50 50 50 42 33 33 17100 100 100 92 92 92 92 83 83
Men 75 67 67 58 58 58 58 50 4242 33
1 How would you analyze and compare the results formen and women??
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Compare and contrast distributions of quantitative data from
two or more groups
Question 2: here are scores from a test I gave to Math 124last semester.
100 100 92 92 83 83 83 83 75Women 75 67 67 67 58 58 58 50 50
50 50 50 42 33 33 17100 100 100 92 92 92 92 83 83
Men 75 67 67 58 58 58 58 50 4242 33
1 How would you analyze and compare the results formen and women??
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Compare and contrast distributions of quantitative data from
two or more groups
Question 2 continued: here are five-number summaries forthe scores from a test I gave to Math 124 last semester.
Min. 1st Qu. Median 3rd Qu. Max.Women 17.00 50.00 67.00 83.00 100.00Men 33.0 58.0 71.0 92.0 100.0
1 Draw the boxplots.2 Would you say that the difference between men and
women was significant?
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Compare and contrast distributions of quantitative data from
two or more groups
Question 2 continued: here are five-number summaries forthe scores from a test I gave to Math 124 last semester.
Min. 1st Qu. Median 3rd Qu. Max.Women 17.00 50.00 67.00 83.00 100.00Men 33.0 58.0 71.0 92.0 100.0
1 Draw the boxplots.
2 Would you say that the difference between men andwomen was significant?
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Compare and contrast distributions of quantitative data from
two or more groups
Question 2 continued: here are five-number summaries forthe scores from a test I gave to Math 124 last semester.
Min. 1st Qu. Median 3rd Qu. Max.Women 17.00 50.00 67.00 83.00 100.00Men 33.0 58.0 71.0 92.0 100.0
1 Draw the boxplots.2 Would you say that the difference between men and
women was significant?
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Produce a two-way table and compare conditional
percentages
Question 3: Here’s some imaginary data.
Explanatory A B A A A B B A B AResponse X Z Z Z X Y X X X X
Explanatory A B B A B A B B A AResponse X X Z Y Z X Y Z X X
• How would you analyze and summarize these datanumerically and graphically?
• Do it.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Produce a two-way table and compare conditional
percentages
Question 3: Here’s some imaginary data.Explanatory A B A A A B B A B A
Response X Z Z Z X Y X X X X
Explanatory A B B A B A B B A AResponse X X Z Y Z X Y Z X X
• How would you analyze and summarize these datanumerically and graphically?
• Do it.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Produce a two-way table and compare conditional
percentages
Question 3: Here’s some imaginary data.Explanatory A B A A A B B A B A
Response X Z Z Z X Y X X X X
Explanatory A B B A B A B B A AResponse X X Z Y Z X Y Z X X
• How would you analyze and summarize these datanumerically and graphically?
• Do it.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Produce a two-way table and compare conditional
percentages
Question 3: Here’s some imaginary data.Explanatory A B A A A B B A B A
Response X Z Z Z X Y X X X X
Explanatory A B B A B A B B A AResponse X X Z Y Z X Y Z X X
• How would you analyze and summarize these datanumerically and graphically?
• Do it.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Interpret the value of the correlation coefficient
• This question is taken from a sample CSET test. CSETis a test that qualifies potential high school mathteachers as competent in mathematics.
• Question 4: Suppose the equation for the regressionline through some data is Y = 4.5 + 2.3X . Then thecorrelation coefficient for the data could be:
1 2.42 0.63 -0.74 -1.3
• If the regression equation was Y = 4.5− 2.3X , whatcould the correlation coefficient be?
• Explain your reasons.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Interpret the value of the correlation coefficient
• This question is taken from a sample CSET test. CSETis a test that qualifies potential high school mathteachers as competent in mathematics.
• Question 4: Suppose the equation for the regressionline through some data is Y = 4.5 + 2.3X . Then thecorrelation coefficient for the data could be:
1 2.42 0.63 -0.74 -1.3
• If the regression equation was Y = 4.5− 2.3X , whatcould the correlation coefficient be?
• Explain your reasons.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Interpret the value of the correlation coefficient
Question 5: Here’s the data from the text relating thelongevity of animals to their gestation period.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Interpret the value of the correlation coefficient
• Is the correlation coefficient for these data positive ornegative?
• Does including the outlier increase or decrease thecorrelation coefficient?
• The correlation with the outlier is 0.66; without theoutlier the correlation is 0.52.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Interpret the value of the correlation coefficient
• Is the correlation coefficient for these data positive ornegative?
• Does including the outlier increase or decrease thecorrelation coefficient?
• The correlation with the outlier is 0.66; without theoutlier the correlation is 0.52.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
In the special case of linear relationship, use the least
squares regression line
Question 6: Here’s a subset of the data from the textrelating the longevity of animals to their gestation period.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
In the special case of linear relationship, use the least
squares regression line
• Is the correlation coefficient for these data positive ornegative?
• Is the correlation coefficient:
1 -0.632 -0.283 0.414 0.755 0.96
• The correlation coefficient is 0.75
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
In the special case of linear relationship, use the least
squares regression line
• Is the correlation coefficient for these data positive ornegative?
• Is the correlation coefficient:
1 -0.632 -0.283 0.414 0.755 0.96
• The correlation coefficient is 0.75
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
In the special case of linear relationship, use the least
squares regression line
The regression equation for these data is Y = 12.9 + 10.3X
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
In the special case of linear relationship, use the least
squares regression line
Question 7:
1 Can you estimate the gestation period for an animalthat lives for 15 years?
2 Can you estimate the gestation period for an animalthat lives for 40 years?
3 Can you estimate the life span of an animal with agestation period of 150 days?
167 days; no, that would require extrapolation; 13.3 years
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
In the special case of linear relationship, use the least
squares regression line
Question 7:
1 Can you estimate the gestation period for an animalthat lives for 15 years?
2 Can you estimate the gestation period for an animalthat lives for 40 years?
3 Can you estimate the life span of an animal with agestation period of 150 days?
167 days; no, that would require extrapolation; 13.3 years
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Recognize and explain the phenomenon of Simpson’s
Paradox
• Simpson’s paradox occurs when data indicates oneconclusion, but when divided into two parts each partindicates the opposite conclusion, or when divided intomany parts most parts indicate the opposite conclusion
• Obviously this cannot happen, but it does• example from UC Bekeley (Wikipedia–Simpson’s
Paradox)http://en.wikipedia.org/wiki/Simpson’s_paradox
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Break
Let’s take a fifteen minute break.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the sampling method used in a study
• A statistical study usually begins with a sample of somesort
• Sample of people from the population you want to study• Sample of rocks from the area you want to study• Sample of blood from the person you want to study
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the sampling method used in a study
• Good types of samples• a simple random sample (selected at random and
without replacement) is, as the name suggests, thesimplest probability sampling plan.
• in cluster sampling we randomly choose whole orentire groups (clusters) of individuals belongingtogether in one way or another, such as taking a simplerandom sample of households and studying allindividuals in each sampled household.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the sampling method used in a study
In stratified sampling we first divide the population intogroups of individuals that are similar to each other in animportant way with respect to the variable of interest (forexample, by gender, or year in college), and then choose asimple random sample from within each group. The groupsare called strata and hence the name "stratified sampling".Using this (a bit more cumbersome) method may help toobtain a representative sample more efficiently.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the sampling method used in a study
Question 8: What kind of study might cluster sampling
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the sampling method used in a study
Whatever kind of sampling you use, a larger sample isusually more accurate than a smaller sample.• Later in this course we study how much improvement a
larger sample can give you• There’s always a trade-off between cost and accuracy.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the sampling method used in a study
• Bad sorts of samples• volunteer sample• convenience sample• wrong sampling frame• systematic sampling
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the sampling method used in a study
• [X ]press’ own unscientific, on-campus exit pollsurveyed 409 people who voted on campus. Sixty-ninepercent of the people polled said they voted for BarackObama while only 20 percent voted for Hillary Clinton.
• Question 10• What kind of sample was this?• How many people voted Republican?
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design of a study (controlled experiment vs.
observational study)
• There are three kinds of statistical studies
• Observational• Experimental• Survey
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design of a study (controlled experiment vs.
observational study)
• There are three kinds of statistical studies• Observational
• Experimental• Survey
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design of a study (controlled experiment vs.
observational study)
• There are three kinds of statistical studies• Observational• Experimental
• Survey
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design of a study (controlled experiment vs.
observational study)
• There are three kinds of statistical studies• Observational• Experimental• Survey
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design and other features of a study
• Observational studies observe variables as theynaturally occur
• Advantage: ecological validity—subjects behavenaturally
• May be negated by subjects’ knowledge that they arebeing observed (Hawthorne effect)
• Hawthorne works of the Western Electric Company inChicago 1924-32
• Disadvantage: difficult to control for lurking variables• For example, if quit-smoking programs are studied by
allowing people to choose one or another quit-smokingmethod spontaneously, then those more determined toquit may tend to choose a different method than thosewho aren’t really trying.
• This will make the method selected by the quitters lookgood
• You overcome this difficulty by conducting an experimentin which people who want to quit smoking are randomlyassigned to different treatments.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design and other features of a study
• Observational studies observe variables as theynaturally occur
• Advantage: ecological validity—subjects behavenaturally
• May be negated by subjects’ knowledge that they arebeing observed (Hawthorne effect)
• Hawthorne works of the Western Electric Company inChicago 1924-32
• Disadvantage: difficult to control for lurking variables• For example, if quit-smoking programs are studied by
allowing people to choose one or another quit-smokingmethod spontaneously, then those more determined toquit may tend to choose a different method than thosewho aren’t really trying.
• This will make the method selected by the quitters lookgood
• You overcome this difficulty by conducting an experimentin which people who want to quit smoking are randomlyassigned to different treatments.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design and other features of a study
• Observational studies observe variables as theynaturally occur
• Advantage: ecological validity—subjects behavenaturally
• May be negated by subjects’ knowledge that they arebeing observed (Hawthorne effect)
• Hawthorne works of the Western Electric Company inChicago 1924-32
• Disadvantage: difficult to control for lurking variables• For example, if quit-smoking programs are studied by
allowing people to choose one or another quit-smokingmethod spontaneously, then those more determined toquit may tend to choose a different method than thosewho aren’t really trying.
• This will make the method selected by the quitters lookgood
• You overcome this difficulty by conducting an experimentin which people who want to quit smoking are randomlyassigned to different treatments.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design and other features of a study
• Observational studies observe variables as theynaturally occur
• Advantage: ecological validity—subjects behavenaturally
• May be negated by subjects’ knowledge that they arebeing observed (Hawthorne effect)
• Hawthorne works of the Western Electric Company inChicago 1924-32
• Disadvantage: difficult to control for lurking variables
• For example, if quit-smoking programs are studied byallowing people to choose one or another quit-smokingmethod spontaneously, then those more determined toquit may tend to choose a different method than thosewho aren’t really trying.
• This will make the method selected by the quitters lookgood
• You overcome this difficulty by conducting an experimentin which people who want to quit smoking are randomlyassigned to different treatments.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design and other features of a study
• Observational studies observe variables as theynaturally occur
• Advantage: ecological validity—subjects behavenaturally
• May be negated by subjects’ knowledge that they arebeing observed (Hawthorne effect)
• Hawthorne works of the Western Electric Company inChicago 1924-32
• Disadvantage: difficult to control for lurking variables• For example, if quit-smoking programs are studied by
allowing people to choose one or another quit-smokingmethod spontaneously, then those more determined toquit may tend to choose a different method than thosewho aren’t really trying.
• This will make the method selected by the quitters lookgood
• You overcome this difficulty by conducting an experimentin which people who want to quit smoking are randomlyassigned to different treatments.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design and other features of a study
• On a test, please don’t limit yourself to saying: “Adisadvantage of observational studies is that they mayfail to uncover lurking variables”.
• Always add: “For example, ...”• Your answer should demonstrate an understanding of
the terms “observational study” and “lurking variable”.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design and other features of a study
• On a test, please don’t limit yourself to saying: “Adisadvantage of observational studies is that they mayfail to uncover lurking variables”.
• Always add: “For example, ...”
• Your answer should demonstrate an understanding ofthe terms “observational study” and “lurking variable”.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Identify the design and other features of a study
• On a test, please don’t limit yourself to saying: “Adisadvantage of observational studies is that they mayfail to uncover lurking variables”.
• Always add: “For example, ...”• Your answer should demonstrate an understanding of
the terms “observational study” and “lurking variable”.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
• Experimental studies put subjects in artificial situationsto observe behavior
• Advantage: can control for lurking variables bycontrolling situation
• Example: studying smoking
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
• Experimental studies put subjects in artificial situationsto observe behavior
• Advantage: can control for lurking variables bycontrolling situation
• Example: studying smoking
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
Disadvantages of experimental studies
• subjects may not behave naturally (lack of ecologicalvalidity)
• Yale University psychologist Stanley Milgram 1963conducted experiment where subjects supposedlyadministered shocks to help learners (who were reallyactors). Learners simulated pain, but subject, on ordersof experimenter kept inflicting greater and greatershocks.
• What did this experiment prove?• Question 11: can you see any ethical problems with this
experiment
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
Disadvantages of experimental studies• subjects may not behave naturally (lack of ecological
validity)
• Yale University psychologist Stanley Milgram 1963conducted experiment where subjects supposedlyadministered shocks to help learners (who were reallyactors). Learners simulated pain, but subject, on ordersof experimenter kept inflicting greater and greatershocks.
• What did this experiment prove?• Question 11: can you see any ethical problems with this
experiment
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
Disadvantages of experimental studies• subjects may not behave naturally (lack of ecological
validity)• Yale University psychologist Stanley Milgram 1963
conducted experiment where subjects supposedlyadministered shocks to help learners (who were reallyactors). Learners simulated pain, but subject, on ordersof experimenter kept inflicting greater and greatershocks.
• What did this experiment prove?• Question 11: can you see any ethical problems with this
experiment
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
Disadvantages of experimental studies• subjects may not behave naturally (lack of ecological
validity)• Yale University psychologist Stanley Milgram 1963
conducted experiment where subjects supposedlyadministered shocks to help learners (who were reallyactors). Learners simulated pain, but subject, on ordersof experimenter kept inflicting greater and greatershocks.
• What did this experiment prove?
• Question 11: can you see any ethical problems with thisexperiment
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
Disadvantages of experimental studies• subjects may not behave naturally (lack of ecological
validity)• Yale University psychologist Stanley Milgram 1963
conducted experiment where subjects supposedlyadministered shocks to help learners (who were reallyactors). Learners simulated pain, but subject, on ordersof experimenter kept inflicting greater and greatershocks.
• What did this experiment prove?• Question 11: can you see any ethical problems with this
experiment
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
Disadvantages of experimental studies• subjects may not behave naturally (lack of ecological
validity)• Yale University psychologist Stanley Milgram 1963
conducted experiment where subjects supposedlyadministered shocks to help learners (who were reallyactors). Learners simulated pain, but subject, on ordersof experimenter kept inflicting greater and greatershocks.
• What did this experiment prove?• Question 11: can you see any ethical problems with this
experiment
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
Blind and double-blind studies, use of placebos areattempts to improve ecological validity of studies
• An experiment is blind if the subject doesn’t know whichtreatment they are receiving
• An experiment is double blind if the subject and thoseadministering the treatments don’t know whichtreatment they are using
• A placebo is a treatment that has no effect. It is used sothat subjects and those administering treatments don’tknow who is in the “no treatment” group.
• Many but not all experiments benefit from the use ofblind and double-blind protocols and the use ofplacebos.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
Blind and double-blind studies, use of placebos areattempts to improve ecological validity of studies• An experiment is blind if the subject doesn’t know which
treatment they are receiving
• An experiment is double blind if the subject and thoseadministering the treatments don’t know whichtreatment they are using
• A placebo is a treatment that has no effect. It is used sothat subjects and those administering treatments don’tknow who is in the “no treatment” group.
• Many but not all experiments benefit from the use ofblind and double-blind protocols and the use ofplacebos.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
Blind and double-blind studies, use of placebos areattempts to improve ecological validity of studies• An experiment is blind if the subject doesn’t know which
treatment they are receiving• An experiment is double blind if the subject and those
administering the treatments don’t know whichtreatment they are using
• A placebo is a treatment that has no effect. It is used sothat subjects and those administering treatments don’tknow who is in the “no treatment” group.
• Many but not all experiments benefit from the use ofblind and double-blind protocols and the use ofplacebos.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
Blind and double-blind studies, use of placebos areattempts to improve ecological validity of studies• An experiment is blind if the subject doesn’t know which
treatment they are receiving• An experiment is double blind if the subject and those
administering the treatments don’t know whichtreatment they are using
• A placebo is a treatment that has no effect. It is used sothat subjects and those administering treatments don’tknow who is in the “no treatment” group.
• Many but not all experiments benefit from the use ofblind and double-blind protocols and the use ofplacebos.
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
More disadvantages of experimental studies
• Subjects may not follow protocols or report inaccurately• Some experiments may be immoral.
• Could you ask a random group of drivers not to useseatbelts?
• Medical experiments are sometimes stoppedmidstream when dangers become clear
• On March 2, 2004, NIH announced that it had stoppedthe estrogen-alone study in the interest of safety aftercareful consideration of preliminary data and an averagefollow-up of nearly 7 years http://www.nhlbi.nih.gov/whi/estro_alone.htm
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
More disadvantages of experimental studies• Subjects may not follow protocols or report inaccurately
• Some experiments may be immoral.• Could you ask a random group of drivers not to use
seatbelts?• Medical experiments are sometimes stopped
midstream when dangers become clear• On March 2, 2004, NIH announced that it had stopped
the estrogen-alone study in the interest of safety aftercareful consideration of preliminary data and an averagefollow-up of nearly 7 years http://www.nhlbi.nih.gov/whi/estro_alone.htm
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
More disadvantages of experimental studies• Subjects may not follow protocols or report inaccurately• Some experiments may be immoral.
• Could you ask a random group of drivers not to useseatbelts?
• Medical experiments are sometimes stoppedmidstream when dangers become clear
• On March 2, 2004, NIH announced that it had stoppedthe estrogen-alone study in the interest of safety aftercareful consideration of preliminary data and an averagefollow-up of nearly 7 years http://www.nhlbi.nih.gov/whi/estro_alone.htm
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
More disadvantages of experimental studies• Subjects may not follow protocols or report inaccurately• Some experiments may be immoral.
• Could you ask a random group of drivers not to useseatbelts?
• Medical experiments are sometimes stoppedmidstream when dangers become clear
• On March 2, 2004, NIH announced that it had stoppedthe estrogen-alone study in the interest of safety aftercareful consideration of preliminary data and an averagefollow-up of nearly 7 years http://www.nhlbi.nih.gov/whi/estro_alone.htm
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Explain how the study design impacts the type of
conclusions that can be drawn
More disadvantages of experimental studies• Subjects may not follow protocols or report inaccurately• Some experiments may be immoral.
• Could you ask a random group of drivers not to useseatbelts?
• Medical experiments are sometimes stoppedmidstream when dangers become clear
• On March 2, 2004, NIH announced that it had stoppedthe estrogen-alone study in the interest of safety aftercareful consideration of preliminary data and an averagefollow-up of nearly 7 years http://www.nhlbi.nih.gov/whi/estro_alone.htm
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
Surveys
• Advantage: Cheap, easy to perform• Disadvantage: must be carefully constructed
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
Surveys
• Advantage: Cheap, easy to perform
• Disadvantage: must be carefully constructed
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
Surveys
• Advantage: Cheap, easy to perform• Disadvantage: must be carefully constructed
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
Problematic survey questions
• limited response options• unbalanced response options• leading questions
• Here’s a real question taken from a political survey:"Some people say (your Democratic incumbent) is astrong supporter of Hillary Clinton and will support herliberal agenda of big government and higher taxes ifshe becomes President. Do you plan to vote for thisperson in November?" (Washington Post, Letter to theEditor, 9/29/07)
• Political surveys like this are called push polls
• planting ideas with questions• complicated questions• sensitive questions
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
Problematic survey questions
• limited response options
• unbalanced response options• leading questions
• Here’s a real question taken from a political survey:"Some people say (your Democratic incumbent) is astrong supporter of Hillary Clinton and will support herliberal agenda of big government and higher taxes ifshe becomes President. Do you plan to vote for thisperson in November?" (Washington Post, Letter to theEditor, 9/29/07)
• Political surveys like this are called push polls
• planting ideas with questions• complicated questions• sensitive questions
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
Problematic survey questions
• limited response options• unbalanced response options
• leading questions• Here’s a real question taken from a political survey:
"Some people say (your Democratic incumbent) is astrong supporter of Hillary Clinton and will support herliberal agenda of big government and higher taxes ifshe becomes President. Do you plan to vote for thisperson in November?" (Washington Post, Letter to theEditor, 9/29/07)
• Political surveys like this are called push polls
• planting ideas with questions• complicated questions• sensitive questions
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
Problematic survey questions
• limited response options• unbalanced response options• leading questions
• Here’s a real question taken from a political survey:"Some people say (your Democratic incumbent) is astrong supporter of Hillary Clinton and will support herliberal agenda of big government and higher taxes ifshe becomes President. Do you plan to vote for thisperson in November?" (Washington Post, Letter to theEditor, 9/29/07)
• Political surveys like this are called push polls
• planting ideas with questions• complicated questions• sensitive questions
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
Problematic survey questions
• limited response options• unbalanced response options• leading questions
• Here’s a real question taken from a political survey:"Some people say (your Democratic incumbent) is astrong supporter of Hillary Clinton and will support herliberal agenda of big government and higher taxes ifshe becomes President. Do you plan to vote for thisperson in November?" (Washington Post, Letter to theEditor, 9/29/07)
• Political surveys like this are called push polls
• planting ideas with questions
• complicated questions• sensitive questions
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
Problematic survey questions
• limited response options• unbalanced response options• leading questions
• Here’s a real question taken from a political survey:"Some people say (your Democratic incumbent) is astrong supporter of Hillary Clinton and will support herliberal agenda of big government and higher taxes ifshe becomes President. Do you plan to vote for thisperson in November?" (Washington Post, Letter to theEditor, 9/29/07)
• Political surveys like this are called push polls
• planting ideas with questions• complicated questions
• sensitive questions
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
Problematic survey questions
• limited response options• unbalanced response options• leading questions
• Here’s a real question taken from a political survey:"Some people say (your Democratic incumbent) is astrong supporter of Hillary Clinton and will support herliberal agenda of big government and higher taxes ifshe becomes President. Do you plan to vote for thisperson in November?" (Washington Post, Letter to theEditor, 9/29/07)
• Political surveys like this are called push polls
• planting ideas with questions• complicated questions• sensitive questions
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
“Randomized responses” to deal with sensitive questions
• Want to ask people if they have done something bad(fill in your own example)
• Tell them to flip a coin and not show it to you• If heads, answer truthfully• If tails, answer “yes”
• At end of study, remove a number of yes answers equalto half the subjects used
• Question 12: Would this method work if the instructionsread: If tails, answer “no”
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
“Randomized responses” to deal with sensitive questions• Want to ask people if they have done something bad
(fill in your own example)
• Tell them to flip a coin and not show it to you• If heads, answer truthfully• If tails, answer “yes”
• At end of study, remove a number of yes answers equalto half the subjects used
• Question 12: Would this method work if the instructionsread: If tails, answer “no”
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
“Randomized responses” to deal with sensitive questions• Want to ask people if they have done something bad
(fill in your own example)• Tell them to flip a coin and not show it to you
• If heads, answer truthfully• If tails, answer “yes”
• At end of study, remove a number of yes answers equalto half the subjects used
• Question 12: Would this method work if the instructionsread: If tails, answer “no”
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
“Randomized responses” to deal with sensitive questions• Want to ask people if they have done something bad
(fill in your own example)• Tell them to flip a coin and not show it to you
• If heads, answer truthfully• If tails, answer “yes”
• At end of study, remove a number of yes answers equalto half the subjects used
• Question 12: Would this method work if the instructionsread: If tails, answer “no”
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
“Randomized responses” to deal with sensitive questions• Want to ask people if they have done something bad
(fill in your own example)• Tell them to flip a coin and not show it to you
• If heads, answer truthfully• If tails, answer “yes”
• At end of study, remove a number of yes answers equalto half the subjects used
• Question 12: Would this method work if the instructionsread: If tails, answer “no”
Math 124:Week 3
Questions andAnswers
Quiz
ReviewStandard Deviation
Review Case I
Review Case II
Review Case III
Sampling
DesigningStudiesObservationalStudies
Experimental Studies
Surveys
Determine how features of a survey impact the collected
data and its accuracy
“Randomized responses” to deal with sensitive questions• Want to ask people if they have done something bad
(fill in your own example)• Tell them to flip a coin and not show it to you
• If heads, answer truthfully• If tails, answer “yes”
• At end of study, remove a number of yes answers equalto half the subjects used
• Question 12: Would this method work if the instructionsread: If tails, answer “no”