Research DesignResearch Design

OperationalizationOperationalizationPsychological Constructs:• Love• Shyness• Hunger• Intelligence• Anxiety• Generosity

OperationalizationOperationalization

Operational Definitions:• Amount of food consumed in one sitting• Number of cigarettes one smokes in an hour• Number of reasoning problems one can solve in 30 minutes• Amount of money someone will spend for a hamburger• Number of conversations initiated with a stranger at a party• Percentage of income donated to charity • Blood pressure, heart rate, respiratory rate, and sweating• Number of friends one claims to have• Agreeing with the statement “I would rather suffer than let

my partner suffer”• Grade received in a psychology course• Number of times someone is thought of during the day

Research DesignResearch Design

• What are the three types of research What are the three types of research design discussed in the book?design discussed in the book?

• Imagine that we are testing a new Imagine that we are testing a new weight loss drug. How would we use weight loss drug. How would we use the three different types of studies to the three different types of studies to investigate weight loss and test its investigate weight loss and test its effectiveness?effectiveness?

Descriptive Studies Descriptive Studies

• Describing behavior w/out Describing behavior w/out investigating relationships between investigating relationships between variablesvariables– Can still be quantitativeCan still be quantitative– Usually used to “get a feel for” a subject Usually used to “get a feel for” a subject

matter or for unusual circumstancesmatter or for unusual circumstances

• Weight loss?Weight loss?

Correlational StudiesCorrelational Studies

• Observe & measure two or more Observe & measure two or more variables to determine how well one variables to determine how well one predicts the otherpredicts the other– No variable manipulationNo variable manipulation– Cannot prove causation. If X & Y are Cannot prove causation. If X & Y are

related:related:•X X Y? or Y Y? or Y X? X?

•Third variable? Z causes X and Y?Third variable? Z causes X and Y?

• Weight loss?Weight loss?

ExperimentsExperiments– Can show Can show causecause and effectand effect

relationships between two variables.relationships between two variables.• Independent variable Independent variable

•Dependent variableDependent variable

– Systematically manipulate the IV to Systematically manipulate the IV to study the changes in the DV. study the changes in the DV.

– Often done in laboratory – not always Often done in laboratory – not always generalizablegeneralizable

– Weight loss?Weight loss?

Elements of an experimentElements of an experiment

• Independent variable Independent variable

• Dependent variable Dependent variable

• Extraneous variables Extraneous variables

• Operational definition Operational definition

• Experimental group Experimental group

• Control group Control group

• Placebo groupPlacebo group

• Random assignment Random assignment

• Single- or double-blind procedure?Single- or double-blind procedure?

Why correlation, then?Why correlation, then?

• Correlation Correlation ≠ Causation.≠ Causation.

• Psychological studies aren’t always Psychological studies aren’t always amenable to experiments for amenable to experiments for practical or ethical reasons.practical or ethical reasons.– Example: Children whose parents have a Example: Children whose parents have a

lot of books in the house are better lot of books in the house are better readers and do better in school.readers and do better in school.

• GeneralizabilityGeneralizability

Mark Twain: “There are three Mark Twain: “There are three kinds of lies: lies, damned kinds of lies: lies, damned

lies, and lies, and statistics”statistics”

In this class, we will deal with the In this class, we will deal with the latter of these three.latter of these three.

Do you agree?Do you agree?

• Men are taller than women.Men are taller than women.

• All men are taller than all women.All men are taller than all women.

• Can you agree with the first Can you agree with the first statement without agreeing with the statement without agreeing with the second??second??

Descriptive statisticsDescriptive statistics

• Used to summarize sets of data Used to summarize sets of data – Make the data accessibleMake the data accessible

• Which is more useful in describing Which is more useful in describing class scores on an exam?class scores on an exam?

A.A. 87, 65, 90, 94, 65, 73, 81, 54, 84, 7587, 65, 90, 94, 65, 73, 81, 54, 84, 75

B.B. Average: 76.8Average: 76.8

Descriptive statisticsDescriptive statistics

• Correlation:Correlation:– correlation coefficientscorrelation coefficients

• Measures of central tendency: Measures of central tendency: – ModeMode– MedianMedian– MeanMean

•Standard deviation (more variable scores = Standard deviation (more variable scores = ↑ SD)↑ SD)

Pretend studyPretend study

• Taking “Taking “IntelligencioIntelligencio”, a new memory ”, a new memory drug, will increase the chances of drug, will increase the chances of doing well in PSY 301 class.doing well in PSY 301 class.

• 1 class, 75 students.1 class, 75 students.– A. 25 took A. 25 took intelligencio, intelligencio, Mean grade: 85Mean grade: 85– B. 25 took placebo, Mean grade: 80B. 25 took placebo, Mean grade: 80– C. 25 took nothing, Mean grade 79C. 25 took nothing, Mean grade 79

Accidental?Accidental?

• Remember: be skepticalRemember: be skeptical

• What other factors could account for What other factors could account for our findings?our findings?

• Are they representative of all Are they representative of all psychology students?psychology students?

Inferential statisticsInferential statistics

• How likely is it that we found a fluke?How likely is it that we found a fluke?

• Inferential statistics help us decide Inferential statistics help us decide this.this.– Depends on:Depends on:

•Size of the effect (large vs. small Size of the effect (large vs. small differences)differences)

•Within-group variance Within-group variance

•Number of observations – helps individual Number of observations – helps individual differences cancel each other out.differences cancel each other out.

Scatterplot data demonstrate Scatterplot data demonstrate correlations:correlations:

Visualizing Various Visualizing Various Scatterplots:Scatterplots:

Two problems with inferences Two problems with inferences of causation from of causation from correlational datacorrelational data

• 1) the directionality problem1) the directionality problem

• 2) the third variable problem2) the third variable problem

Illustrating the directionality Illustrating the directionality and third variable problemsand third variable problems

• Neurotransmitter metabolites of Neurotransmitter metabolites of Norepinephrine and Serotonin have a Norepinephrine and Serotonin have a moderate negative correlation with moderate negative correlation with level of clinical depression, but what level of clinical depression, but what causes what?causes what?

Is depression caused by Is depression caused by low levels of NE and 5-HT?low levels of NE and 5-HT?

• The following scatterplot empirically The following scatterplot empirically characterizes the moderate negative characterizes the moderate negative correlation between depression and correlation between depression and levels of Norepinephrine (NE) and levels of Norepinephrine (NE) and Serotonin (5-HT) metabolitesSerotonin (5-HT) metabolites

• Question to frame the discussion: Do Question to frame the discussion: Do the data support the “biogenic amine” the data support the “biogenic amine” theory of depression?theory of depression?

The directionality problem in The directionality problem in the metabolite scatterplot:the metabolite scatterplot:

• Direction 1 (Pharmaceutical-Friendly): Direction 1 (Pharmaceutical-Friendly):

• Insufficient neurotransmitters cause Insufficient neurotransmitters cause depression (the biogenic amine theory)depression (the biogenic amine theory)

• Direction 2 (favored by anti-drug groups):Direction 2 (favored by anti-drug groups):

•Maybe depression causes biochemical Maybe depression causes biochemical deficiencies instead of vice versa?deficiencies instead of vice versa?

The third variable look at the The third variable look at the biogenic amine theory:biogenic amine theory:

•Maybe a third variable (or set of Maybe a third variable (or set of variables) cause(s) both variables) cause(s) both biochemical dysregulation and biochemical dysregulation and depression? depression?

•What does the correlation tell us, What does the correlation tell us, then?then?

– The variables are associated and The variables are associated and we need to figure out whywe need to figure out why

What are the data collection What are the data collection methods of psychological methods of psychological science?science?• Observing is an unobtrusive strategyObserving is an unobtrusive strategy• Asking takes a more active approachAsking takes a more active approach• Case studies examine individual livesCase studies examine individual lives• Response performance measures Response performance measures

stimulus processingstimulus processing• Body and brain activity can be directly Body and brain activity can be directly

measuredmeasured• Research with animals provides Research with animals provides

important dataimportant data• There are ethical issues to considerThere are ethical issues to consider

Descriptive studiesDescriptive studies

• Descriptive studiesDescriptive studies, sometimes , sometimes called observational studies because called observational studies because of the manner in which the data are of the manner in which the data are typically collected, involve observing typically collected, involve observing and noting behavior in order to and noting behavior in order to provide a systematic and objective provide a systematic and objective analysisanalysis

Observing is an Observing is an unobstrusive strategyunobstrusive strategy

• Primate behavior is often observed in Primate behavior is often observed in natural settings.natural settings.

• Animals are more likely to act Animals are more likely to act naturally when they are in their naturally when they are in their native habitat, relative to animals in native habitat, relative to animals in captivity.captivity.

Asking takes a more Asking takes a more active approachactive approach

Case studies examine Case studies examine individual livesindividual lives

• For example, many psychologists For example, many psychologists think that immature brain think that immature brain development, in combination with development, in combination with other factors, contributes to violent other factors, contributes to violent behavior. behavior.

• Lee Boyd Malvo and Kip Kinkel were Lee Boyd Malvo and Kip Kinkel were both convicted of murder in their both convicted of murder in their teens.teens.

Response performance Response performance measures stimulus measures stimulus processingprocessing• Researchers can measure:Researchers can measure:

– Reaction timeReaction time– Response accuracyResponse accuracy– Stimulus judgmentsStimulus judgments

Body and brain activity can Body and brain activity can be directly measuredbe directly measured

Positron Emission Tomography (PET)Positron Emission Tomography (PET)

A PET scan of blood flow in a subject’s brain A PET scan of blood flow in a subject’s brain under different conditions.under different conditions.

Magnetic Resonance Imaging Magnetic Resonance Imaging (MRI)(MRI)

MRI provides very high quality images MRI provides very high quality images

of intact human brains.of intact human brains.

Fig. 2.9Fig. 2.9

Research with animals Research with animals provides important dataprovides important data

• Throughout the history of Throughout the history of psychological science, many psychological science, many important research findings have important research findings have been obtained by studying animals.been obtained by studying animals.

There are ethical issues to There are ethical issues to considerconsider• IRB’sIRB’s

• Informed consentInformed consent

• Relative risks of participationRelative risks of participation

• Research with animalsResearch with animals

How are data analyzedHow are data analyzedand evaluated?and evaluated?

• • Good research requires valid, reliable,Good research requires valid, reliable,and accurate dataand accurate data

• • Descriptive statistics provide a summaryDescriptive statistics provide a summary

• • Correlations describe the relationshipsCorrelations describe the relationshipsbetween variablesbetween variables

• • Inferential statistics predict chanceInferential statistics predict chanceresultsresults

Good research requires valid, Good research requires valid, reliable, and accurate datareliable, and accurate data

• Validity: whether the data address the Validity: whether the data address the research question unambiguouslyresearch question unambiguously

• Reliability: stability and consistency of a Reliability: stability and consistency of a measure over timemeasure over time

• Accuracy: the extent to which the measure Accuracy: the extent to which the measure is free from erroris free from error

Descriptive statistics Descriptive statistics provide a summaryprovide a summary

• Central TendenceCentral Tendence– MeanMean– MedianMedian– ModeMode

• VariabilityVariability– Standard deviationStandard deviation

Correlations describe the Correlations describe the relationships between relationships between variablesvariables- Correlation is a descriptive statistic Correlation is a descriptive statistic

that gives a numerical value that gives a numerical value (between +1.0 and -1.0) indicating (between +1.0 and -1.0) indicating the strength of a relationship the strength of a relationship between 2 variables.between 2 variables.- Negative correlationNegative correlation- Positive correlationPositive correlation

Inferential statistics Inferential statistics predict chance resultspredict chance results

- Researchers use inferential statistics Researchers use inferential statistics to decide whether differences to decide whether differences actually exist between different sets actually exist between different sets of numbers.of numbers.

Types of ErrorTypes of Error

• RandomRandom

• SystematicSystematic