Psychological Psychological Research Methods & Research Methods &

StatisticsStatistics

Excavating Human Behaviors

Psychology & Research Psychology & Research MethodsMethods

A “Scientific Attitude” is critical…A “Scientific Attitude” is critical… CuriosityCuriosity – a passion to explore and understand. – a passion to explore and understand. SkepticismSkepticism – psychologists, like other scientists, – psychologists, like other scientists,

approach the world of behavior with curious approach the world of behavior with curious doubt. They are constantly asking two doubt. They are constantly asking two questions: What does it mean? How do you questions: What does it mean? How do you know?know?

HumilityHumility – an awareness and acceptance that – an awareness and acceptance that we may have to reject our own ideas or we may have to reject our own ideas or theories (if they are proven wrong).theories (if they are proven wrong).

Critical ThinkingCritical Thinking – a scientific approach – a scientific approach prepares/demands us to think “smarter” prepares/demands us to think “smarter” to to examine assumptions, evaluate evidence, and examine assumptions, evaluate evidence, and assess conclusions.assess conclusions.

Hindsight BiasHindsight Bias

The tendency to The tendency to believe, after believe, after learning the learning the outcome, that you outcome, that you knew it all along.knew it all along.

With 20/20 With 20/20 hindsight, hindsight, everything seems everything seems obvious.obvious.

OverconfidenceOverconfidenceWe tend to think we know more We tend to think we know more

than we dothan we do..We tend to be more confident We tend to be more confident

than correct!than correct!82% of U.S. drivers consider themselves

to be in the top 30% of their group in terms of safety

81% of new business owners felt they had an excellent chance of their

businesses succeeding. When asked about the success of their peers, the answer was only 39%. (Now that's

overconfidence!!!)

Exercise:Exercise: Unscramble these Unscramble these AnagramsAnagrams

WREATWREATETRYNETRYNGRABEGRABE

Anagram SolutionsAnagram Solutions

WREAT --- WATERWREAT --- WATERETRYN --- ENTRYETRYN --- ENTRYGRABE --- BARGEGRABE --- BARGE

Psychological Research Psychological Research MethodsMethods

Psychology is an experimental science.Psychology is an experimental science. Assumptions must be supported by evidence.Assumptions must be supported by evidence. Psychologists use a variety of research methods Psychologists use a variety of research methods

to study behavior and mental processes.to study behavior and mental processes. Psychologists follow the same general Psychologists follow the same general

procedure when conducting research:procedure when conducting research:1.1. Asking research questionsAsking research questions2.2. Forming hypothesis (hypotheses)Forming hypothesis (hypotheses)3.3. Testing the hypothesesTesting the hypotheses4.4. Analyzing the data (results)Analyzing the data (results)5.5. And drawing conclusionsAnd drawing conclusions6.6. Eventually, replicating researchEventually, replicating research

The Scientific The Scientific MethodMethod

Step 1: Forming research questions – Step 1: Forming research questions – Beginning with scientific curiosity and interest, many Beginning with scientific curiosity and interest, many

research questions come from daily experience, research questions come from daily experience, psychological theory, or common knowledge. psychological theory, or common knowledge.

Step 2: Forming hypotheses – Step 2: Forming hypotheses – An An hypothesishypothesis is a statement of that which you wish is a statement of that which you wish

to prove.to prove. An hypothesis is a predicted “answer” to the question An hypothesis is a predicted “answer” to the question

(or in the words of some researchers, “an educated (or in the words of some researchers, “an educated guess”).guess”).

The Scientific MethodThe Scientific Method

Step 3: Testing hypotheses –Step 3: Testing hypotheses –1.1.Once a hypothesis has been formed, it must be Once a hypothesis has been formed, it must be

scientifically tested and proved right or wrong.scientifically tested and proved right or wrong.

2.2.This part of conducting research is the “actual” This part of conducting research is the “actual” experiment.experiment.

3.3.Psychologists use a Psychologists use a variety of methodsvariety of methods to test to test hypotheses.hypotheses.

Step 4: Analyzing Results – Step 4: Analyzing Results – 1.1.Data is analyzed using statistics.Data is analyzed using statistics.

2.2.The more data collected, The more data collected,

the more complex a task the more complex a task

it is to analyze.it is to analyze.

The Scientific MethodThe Scientific Method• Step 5: Drawing Conclusions – Step 5: Drawing Conclusions –

• Once the results have been analyzed, a Once the results have been analyzed, a psychologist can draw or make conclusions about psychologist can draw or make conclusions about his/her questions and hypotheses.his/her questions and hypotheses.

• Step 6: Replication – Step 6: Replication – 1.1. Even when a research study carefully follows Even when a research study carefully follows

proper procedures, its findings might just proper procedures, its findings might just represent a random occurrence.represent a random occurrence.

2.2. To confirm the results and conclusions of a To confirm the results and conclusions of a research study, the study must be replicated.research study, the study must be replicated.

3.3. The study must be repeated and it must produce The study must be repeated and it must produce the same or similar results as before.the same or similar results as before.

4.4. If there are different results, then the findings of If there are different results, then the findings of the first study are questioned.the first study are questioned.

Selecting SubjectsSelecting Subjects

PopulationPopulation – all members of a given group – all members of a given group (within the study).(within the study).

SampleSample – a subset of the population which – a subset of the population which is representative of the whole population.is representative of the whole population.

Random SampleRandom Sample – a sample in which every – a sample in which every member of the population has an equal member of the population has an equal chance of being selected.chance of being selected.

Stratified SampleStratified Sample – a sample in which each – a sample in which each subgroup of the population is represented subgroup of the population is represented proportionally to its size in the population.proportionally to its size in the population.

Key Research Key Research TerminologyTerminology

Using a Using a random samplerandom sample that represents that represents the whole population, a researcher can the whole population, a researcher can generalize findings to the entire generalize findings to the entire population.population.

CAUTION: CAUTION: OvergeneralizationOvergeneralization – is the – is the making of generalizations using making of generalizations using unrepresentative cases. It is easy to do unrepresentative cases. It is easy to do but typically erroneous.but typically erroneous.

False Consensus EffectFalse Consensus Effect:: the tendency to the tendency to overestimate the extent to which others overestimate the extent to which others share our beliefs and behaviorsshare our beliefs and behaviors

Methods of Collecting Methods of Collecting DataData

SurveySurvey – commonly used in both – commonly used in both descriptive and correlational studies, descriptive and correlational studies, questionnaire method sampling many questionnaire method sampling many cases (individuals) in less depth cases (individuals) in less depth

Case StudyCase Study – the study of one or more – the study of one or more individuals in great depth, to inform about individuals in great depth, to inform about an entire population or samplean entire population or sample

TestingTesting – psychological tests are given to – psychological tests are given to measure certain mental processes, such measure certain mental processes, such as intelligence, aptitude, or personalityas intelligence, aptitude, or personality

The Survey MethodThe Survey Method

Used in both descriptional and Used in both descriptional and correlational research.correlational research.

Use Interview, mail, phone, internet Use Interview, mail, phone, internet etc…etc…

The Good-The Good- cheap, anonymous, diverse cheap, anonymous, diverse population, and easy to get population, and easy to get random random samplingsampling (a sampling that represents (a sampling that represents your population you want to study)your population you want to study)

Survey Method: The BadSurvey Method: The Bad

Low Response Low Response RateRate

People Lie or People Lie or just just misinterpret misinterpret themselves.themselves.

Wording Wording EffectsEffects

How accurate would a survey be about the frequency of diarrhea?

Naturalistic ObservationNaturalistic Observation

Observing and Observing and recording behaviors of recording behaviors of an organism in natural an organism in natural environmentenvironment

No control- just an No control- just an observerobserver

This method does not This method does not explain behavior but explain behavior but describes itdescribes itWhat are the benefits and detriments of Naturalistic Observation?

Methods of Collecting Methods of Collecting DataData

Laboratory ObservationLaboratory Observation – this research – this research method involves watching and recording method involves watching and recording behaviors of organisms behaviors of organisms NOTNOT in their natural in their natural environment environment BUTBUT in a laboratory setting. in a laboratory setting.

Cross-sectional StudiesCross-sectional Studies – uses participants – uses participants (subjects) of different ages to compare how (subjects) of different ages to compare how certain variables may change over the life certain variables may change over the life span.span.Longitudinal StudiesLongitudinal Studies – use one group of – use one group of participants over a long period of time. This participants over a long period of time. This method of study tracks the change over time method of study tracks the change over time of the participants.of the participants.

Correlational ResearchCorrelational Research Detects relationships between variablesDetects relationships between variables Does NOT say that one variable causes Does NOT say that one variable causes

anotheranother

There is a positive correlation between ice cream and murder rates. Does that mean that ice cream causes murder?

Correlation Correlation vs.vs. Cause & Cause & EffectEffect

Correlation coefficientCorrelation coefficient is a statistical is a statistical measure of relationship (it reveals how measure of relationship (it reveals how closely related two factors are or how closely related two factors are or how closely two factors vary together and thus closely two factors vary together and thus how well either one predicts the other).how well either one predicts the other).

PositivePositive and and negativenegative correlations are correlations are possiblepossible

A relationship A relationship does notdoes not mean mean causation!!!causation!!!• For example, watching TV violence positively For example, watching TV violence positively

correlates with aggressive behavior; but correlates with aggressive behavior; but does does notnot necessarily mean watching violence on TV necessarily mean watching violence on TV causes aggressive behavior.causes aggressive behavior.

How to Read a Correlation How to Read a Correlation CoefficientCoefficient

Experimental ResearchExperimental Research

Explores cause and effect relationshipsExplores cause and effect relationships

Eating too many bananas causes Constipation

Experimental ResearchExperimental Research In an experiment, participants In an experiment, participants

receive what is called a treatment, receive what is called a treatment, such as a change in room such as a change in room temperature or a new drug.temperature or a new drug.

Then, psychologists carefully observe Then, psychologists carefully observe the participants to determine how the participants to determine how the treatment influences their the treatment influences their behavior.behavior.

Independent and Independent and Dependent VariablesDependent Variables

All research studies measure and All research studies measure and observe variables (factors), especially observe variables (factors), especially experimental studies.experimental studies.

In an experiment, the In an experiment, the independent independent variablevariable is the factor that the is the factor that the researcher manipulates (controls) so researcher manipulates (controls) so that they can determine its that they can determine its effecteffect on on the dependent variable.the dependent variable.

The The dependent variabledependent variable is the is the factor that depends on the factor that depends on the manipulated independent variable(s).manipulated independent variable(s).

Experimental and Control Experimental and Control GroupsGroups

The The experimental groupexperimental group is a group of participants is a group of participants who receive the treatment or manipulated variable.who receive the treatment or manipulated variable.

The The control groupcontrol group is a group of participants who do is a group of participants who do not receive the manipulated variable (instead a not receive the manipulated variable (instead a placebo of sorts).placebo of sorts).

All other variables/factors are held constant (or All other variables/factors are held constant (or equal) for both groups (to try to isolate a cause and equal) for both groups (to try to isolate a cause and effect relationship between independent variable(s) effect relationship between independent variable(s) of interest to the research psychologist and the of interest to the research psychologist and the dependent variable.dependent variable.

If the research psychologist fails to manage the If the research psychologist fails to manage the ‘other’ variables (or hold them constant), they ‘other’ variables (or hold them constant), they become become confoundingconfounding variablesvariables. Confounding . Confounding variables are baaaaad!!!variables are baaaaad!!!

Experimental MethodExperimental Method continuedcontinued Psychologists randomly place participants (subjects) Psychologists randomly place participants (subjects)

into one group or another.into one group or another.– EXAMPLE: The effect of extracurricular activities on student’s EXAMPLE: The effect of extracurricular activities on student’s

academic success.academic success. Once subjects are randomly placed into the control Once subjects are randomly placed into the control

and experimental groups, the researcher makes sure and experimental groups, the researcher makes sure that all other variables are the same for all students that all other variables are the same for all students regardless of group.regardless of group.

Using this grouping method in the experimental Using this grouping method in the experimental method is called a controlled experiment.method is called a controlled experiment.

The Placebo EffectThe Placebo Effect In research studies and in our daily lives, our In research studies and in our daily lives, our

expectations affect what happens to us.expectations affect what happens to us. Feeling better simply because we expect to feel better Feeling better simply because we expect to feel better

and for no other reason is an example of the placebo and for no other reason is an example of the placebo effect.effect.

A placebo is a substance or treatment that has no A placebo is a substance or treatment that has no effect apart from the person’s belief in it.effect apart from the person’s belief in it.

Experimental MethodExperimental Method continuedcontinued

Single-blind vs. Double-blind StudiesSingle-blind vs. Double-blind Studies In a In a single-blind studysingle-blind study, participants do , participants do

not know whether they are receiving the not know whether they are receiving the treatment (the manipulated independent treatment (the manipulated independent variable) or not. In other words, they do variable) or not. In other words, they do not know if they are in the experimental not know if they are in the experimental group or in the control group.group or in the control group.

This process avoids the placebo effect.This process avoids the placebo effect. In a In a double-blind studydouble-blind study, both , both

participants and researchers are unaware participants and researchers are unaware of who has placed in which group.of who has placed in which group.

Statistics & Research MethodsStatistics & Research Methods

Describing (Quantifying) DataDescribing (Quantifying) Data ScalingScaling – assigning numbers to observed – assigning numbers to observed

events (responses, etc.)events (responses, etc.) Categorical Scale (Nominal)Categorical Scale (Nominal) – a number/score – a number/score

is assigned to individuals so as to group is assigned to individuals so as to group responses into categories (example: gender)responses into categories (example: gender)

Ordinal ScaleOrdinal Scale – assigning numbers to convey – assigning numbers to convey relative meaning among responses (example: relative meaning among responses (example: making a list from “most” to “least”making a list from “most” to “least”

Interval ScaleInterval Scale – assigning numbers/scores in – assigning numbers/scores in which equal differences can be treated as which equal differences can be treated as equal units (example: reaction time)equal units (example: reaction time)

Ratio ScaleRatio Scale – relative scores assigned by way – relative scores assigned by way of multiples and includes a true zero point of multiples and includes a true zero point (example: 15 is 3 times greater than 5)(example: 15 is 3 times greater than 5)

Statistics & Research Statistics & Research MethodsMethods Frequency Distribution – a set of data that tells you how many…Frequency Distribution – a set of data that tells you how many…

Descriptive StatisticsDescriptive StatisticsMeasures of Central TendencyMeasures of Central Tendency Mark the center of a distribution Mark the center of a distribution Mean, Median, Mode Mean, Median, Mode MeanMean – is average of all the scores in a distribution – is average of all the scores in a distribution MedianMedian – is the central score in a distribution – is the central score in a distribution ModeMode – is the score that appears most frequently – is the score that appears most frequently The mean is the most commonly used measure of central tendency, but The mean is the most commonly used measure of central tendency, but

its accuracy can be distorted by extreme scores or its accuracy can be distorted by extreme scores or outliersoutliers. .

Measures of VariabilityMeasures of Variability RangeRange – is the distance between the highest and lowest scores in a – is the distance between the highest and lowest scores in a

distribution.distribution. VarianceVariance – is the amount of difference/variability between scores in a – is the amount of difference/variability between scores in a

distribution.distribution. Standard deviationStandard deviation – is simply the square root of the variance (Both – is simply the square root of the variance (Both

variance and standard deviation relate the average distance of any variance and standard deviation relate the average distance of any score in the distribution from the mean).score in the distribution from the mean).

Z-scoresZ-scores – measure the distance of a score from the mean in units of – measure the distance of a score from the mean in units of standard deviation (to compare scores from different distributions).standard deviation (to compare scores from different distributions).

Normal DistributionNormal Distribution or or Normal CurveNormal Curve or or Bell-shaped CurveBell-shaped Curve – – approx. 68% of scores in a normal distribution fall within one standard approx. 68% of scores in a normal distribution fall within one standard deviation of the mean and approx. 95% of scores fall within two deviation of the mean and approx. 95% of scores fall within two standard deviation of the mean.standard deviation of the mean.

Statistics & Research Statistics & Research MethodsMethodsInferential StatisticsInferential Statistics

While descriptive statistics provide a way to summarize While descriptive statistics provide a way to summarize information about a sample studied, the purpose of information about a sample studied, the purpose of inferential statistics is to determine whether or not inferential statistics is to determine whether or not findings can be applied to the larger population from findings can be applied to the larger population from which the sample was selected. which the sample was selected.

The extent to which the sample differs from the population The extent to which the sample differs from the population is known as sampling error.is known as sampling error.

A few inferential statistical tests exist such as t-tests, A few inferential statistical tests exist such as t-tests, ANOVAs, and MANOVAs. ANOVAs, and MANOVAs.

These tests take into account both the magnitude of the These tests take into account both the magnitude of the difference found and the size of the sample.difference found and the size of the sample.

All these tests yield a All these tests yield a p valuep value. The smaller the p value, the . The smaller the p value, the more significant the results. more significant the results.

P value of .05 is the cutoff for statistically significant P value of .05 is the cutoff for statistically significant results. (p value of .05 means that a 5% chance exists that results. (p value of .05 means that a 5% chance exists that the results occurred by chance. the results occurred by chance.

P value of .01 is sometimes sought for greater certainty of P value of .01 is sometimes sought for greater certainty of significant results. significant results.

P value can never equal 0 because one can never be 100% P value can never equal 0 because one can never be 100% certain that results did not happen randomly by chance.certain that results did not happen randomly by chance.

Replication allows for greater certainty of results.Replication allows for greater certainty of results.

Statistics & Research Statistics & Research MethodsMethods

Null hypothesisNull hypothesis: (: (HH0) is a hypothesis 0) is a hypothesis (scenario) set up to be nullified, refuted, (scenario) set up to be nullified, refuted, or rejected ('disproved' statistically) in or rejected ('disproved' statistically) in order to support an order to support an alternative hypothesisalternative hypothesis

Type I errorType I error: the error of rejecting a : the error of rejecting a null hypothesisnull hypothesis when it is actually true when it is actually true

Type II errorType II error: the error of failing to : the error of failing to reject a null hypothesis when the reject a null hypothesis when the alternative hypothesis is the true state of alternative hypothesis is the true state of nature nature

T-testT-test The t-test assesses whether the The t-test assesses whether the

means of two groups are means of two groups are statisticallystatistically different from each other. This different from each other. This analysis is appropriate whenever you analysis is appropriate whenever you want to compare the means of two want to compare the means of two groupsgroups

www.graphpad.com/quickcalcs/www.graphpad.com/quickcalcs/ttestttest1.cfm1.cfm

X = mean of groupX = mean of group

Var = Standard deviation of groupVar = Standard deviation of group

N = number in sampleN = number in sample

Research & Statistics Research & Statistics Assignment 1Assignment 1

Gather shoe size data from 10 females Gather shoe size data from 10 females and 10 males, recording the shoe size of and 10 males, recording the shoe size of each.each.

Then calculate the measures of central Then calculate the measures of central tendency (mean, mode, median) and tendency (mean, mode, median) and graph the data set in a frequency graph the data set in a frequency histogram and box-plot.histogram and box-plot.

Find and discuss any outliersFind and discuss any outliers Explain the gender difference, if one Explain the gender difference, if one

exists.exists.

Research & Statistics Research & Statistics Assignment 2Assignment 2

Using the Research Question: How many pairs Using the Research Question: How many pairs of shoes do males and females own? Write a of shoes do males and females own? Write a testable hypothesis.testable hypothesis.

Next, gather data from 10 females and 10 Next, gather data from 10 females and 10 males, recording the number of shoes owned males, recording the number of shoes owned by each.by each.

Ask your participants, “How many pairs of Ask your participants, “How many pairs of shoes do you own?” and (obviously) record shoes do you own?” and (obviously) record their answer and gender.their answer and gender.

Calculate the measures of central tendency Calculate the measures of central tendency and standard deviation and test for differences and standard deviation and test for differences between means using a t-test. (use between means using a t-test. (use www.graphpad.com/quickcalcs/www.graphpad.com/quickcalcs/ttestttest1.cfm1.cfm to to help you calculate a t-score)help you calculate a t-score)

Write a brief conclusion about your results (at Write a brief conclusion about your results (at least 1 paragraph). Make sure you give an least 1 paragraph). Make sure you give an explanation for the differences between the explanation for the differences between the gender. gender.