statistical reasoning for everyday life

Statistical Reasoningfor everyday life

Intro to Probability and Statistics

Mr. Spering – Room 113

1.4 Believing Statistics??

Check IN????Have you ever heard an unbelievable statistic

or claim? How did you react?

Research Shows????? Show me the research? When should you believe a statistical study?


Most researchers conduct studies with honesty and integrity

However, bias can arise in many ways. Thus we examine statistics carefully, looking for anything that might cause question. “BE METICULOUS!”

No definitive way to ask “Should I believe a statistical study?”

Nevertheless, the following guidelines can be helpful.

1.4 Believing Statistics?? Eight Guidelines for Evaluating a Study

1. Identify the goal, population, and type of study2. Consider the source, are they biased3. Question the sampling method, “Is it

representative?”4. Look for problems in defining or measuring

variables of interest5. Watch for confounding factors that can invalidate

conclusions

TO BE CONTINUED….

1.4 Believing Statistics?? Eight Guidelines for Evaluating a Study

6. Consider any survey, looking for anything that might produce inaccurate or dishonest results

7. Check that results are fairly represented in graphs and concluding statements, both researchers and media often create misleading graphics or jump to conclusions not supported by results.

8. Finally, consider the conclusions. Do the conclusions make sense? Do the results have any particular significance? Did the study achieve its goals?

Use your own judgments to extend these guidelines!


Bizarre Factoid:

Statistic: 3% of pet owners give

Valentine's gifts to their pets on Valentine's Day.

???

The only guy without a beard in the band ZZTOP is….

Frank Beard


Consider the source: Help prevent problem studies by using Peer Review.Peer review – Process in which several

experts in a field evaluate a research report before the report is published.


Examine the Sampling Method: Poor sampling methods almost guarantee bias. (GALLUP)

Check for these confounding factors – Selection bias (selection effect) – occurs when

sample chosen in biased way Participation bias – occurs when subjects in study are

voluntary Voluntary response survey – remember self-selected

survey and convenience sampling


Variable – item or quantity that can vary or take on different values

Variables of interest – items or quantities that the study seeks to measure

Problems in defining or measuring variables: Results of statistical studies are harder to interpret and seem viable if the variables under study are difficult to define or measure


Watch out for confounding variables:

Often, other variables that are not part of the study can make it difficult to interpret results.

Confounding factors → confounding variables

Confounding variables can affect a study’s results if they have not been accounted for, they are difficult to discover, and sometimes they are never discovered.


Consider the wording of a survey:

Unfortunately most people do not have a problem with lying → avoid sensitive subjects

Availability error – people are more likely to choose the item that comes first in a survey because of a tendency to make judgments on what is most available in the mind.


Stand back and consider the conclusions: Did the study achieve its goals? Do the conclusions make sense? Can you rule out alternative explanations? If conclusions make sense, do they have

significance? (i.e. losing half a pound, killing 5 bacteria, saving 2 minutes)

Extraordinary claims require extraordinary evidence!

-Carl Sagan


Why is a self-selected survey always prone to bias?

People who feel strongly about an issue are more likely to respond, therefore the opinions of the respondents is unlikely to represent the opinions of a larger population.

What are confounding variables?Confounding factors


HOMEWORK # 4: pg 42 # 6-30 even

BE INQUSITIVE!

statistical reasoning for everyday life

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