Research Methods for the Social Sciences: An Introductory Course

Research Methods for Research Methods for the Social Sciences:the Social Sciences:

An Introductory CourseAn Introductory Course

March 1March 1stst, 2010 – More on Design: , 2010 – More on Design: CausalityCausality

Division on Addictions, Cambridge Health AllianceDivision on Addictions, Cambridge Health AllianceHarvard Medical SchoolHarvard Medical School

AgendaAgenda

Revisiting Research DesignRevisiting Research Design– Experimental vs. Quasi-ExperimentalExperimental vs. Quasi-Experimental– Longitudinal DesignsLongitudinal Designs

Prevalence vs. Incidence / Individual Prevalence vs. Incidence / Individual TrajectoriesTrajectories

Moderation and MediationModeration and Mediation Sample StudiesSample Studies

Caveat: Caveat: Association Does Not Equal CausationAssociation Does Not Equal Causation

Correlate Does Not Equal Correlate Does Not Equal DeterminantDeterminant

MMR – Autism Link?MMR – Autism Link?

Correlation vs. ExperimentCorrelation vs. Experiment

Correlational researchCorrelational research– Goal: To describe relationship between Goal: To describe relationship between

two or more variables.two or more variables.– NO CAUSALITYNO CAUSALITY

Experimental researchExperimental research– Goal: Cause-and-effect relationship Goal: Cause-and-effect relationship

between variablesbetween variables

Adapted from Dr. Braverman’s slides

Does Caffeine Increase Does Caffeine Increase Blood Pressure?Blood Pressure?

WRONG ApproachWRONG Approach– Ask participants (or Ask participants (or

observe) how many observe) how many cups of coffee they cups of coffee they drink drink

– Measure blood Measure blood pressurepressure

– Calculate the Calculate the correlation coefficientcorrelation coefficient

RIGHT ApproachRIGHT Approach– Manipulate amount Manipulate amount

of coffeeof coffee Experimental group – Experimental group –

drinkdrink Control group – do not Control group – do not

drinkdrink

– Random group Random group assignmentassignment

– Test difference Test difference between groups between groups


Properties of an ExperimentProperties of an Experiment

1.1. Manipulate at least 1 independent Manipulate at least 1 independent variablevariable

2.2. Assign participants to the various Assign participants to the various conditions in a way that assures conditions in a way that assures their initial equivalencetheir initial equivalence

3.3. Control extraneous variablesControl extraneous variables


Assignment of Participants Assignment of Participants to Conditionsto Conditions

Simple random assignment (Between Simple random assignment (Between Group)Group)– Every participant has equal probability of being Every participant has equal probability of being

placed in any experimental condition.placed in any experimental condition. Matched Random assignment (Between Matched Random assignment (Between

Group)Group)– Participants are assigned to groups based on Participants are assigned to groups based on

their score on a relevant measure. their score on a relevant measure. Repeated measures (Within group)Repeated measures (Within group)

– Same participant is assigned to different Same participant is assigned to different conditions.conditions.


Control Extraneous Control Extraneous VariablesVariables

Eliminate or hold constant factors Eliminate or hold constant factors (confounds)(confounds), other than IV that may , other than IV that may affect the outcomes of the affect the outcomes of the experiment.experiment.– If these factors are random, they create If these factors are random, they create

noise that can mask any effectsnoise that can mask any effects– If they vary systematically with If they vary systematically with

condition, they can create confoundscondition, they can create confounds


Types of variableTypes of variable

Dependent variables – OBSERVEDDependent variables – OBSERVED Independent variables – Independent variables –

MANIPULATEDMANIPULATED Control variables – held CONSTANTControl variables – held CONSTANT


Quasi-ExperimentQuasi-Experiment

1.1. No IV manipulation.No IV manipulation.

2.2. No random group assignment. No random group assignment.


Type 1. Pretest-Posttest DesignType 1. Pretest-Posttest Design

O1 – pretest measure of students’ O1 – pretest measure of students’ drug usedrug use

X – interventionX – intervention O2 – posttest measure of drug use.O2 – posttest measure of drug use.

O1 X O2


Type 1. Pretest-Posttest Type 1. Pretest-Posttest Design.Design.

Weaknesses.Weaknesses. Extraneous variables (History effect)Extraneous variables (History effect)

– Something else affected the IV Something else affected the IV Maturation effectMaturation effect

– Students grew up.Students grew up. Regression to the meanRegression to the mean

– The tendency for extreme scores to move, The tendency for extreme scores to move, or regress toward the mean (because of or regress toward the mean (because of measurement error).measurement error).

AttritionAttrition– Some subjects may drop out before Some subjects may drop out before

posttest.posttest.Adapted from Dr. Braverman’s slides

Type 2. Simple Interrupted Type 2. Simple Interrupted Time-Series DesignTime-Series Design

O1 O2 O3 O4 X O5 O6 O7 O8O1 O2 O3 O4 X O5 O6 O7 O8 Taking several pretest measures of Taking several pretest measures of

the DV before introducing an IV. And the DV before introducing an IV. And then, taking several posttest then, taking several posttest measures. measures.


Type 2. Simple Interrupted Type 2. Simple Interrupted Time-Series DesignTime-Series Design

O1 O2 O3 O4 O5 O6 O7 O8

X

O1 O2 O3 O4 O5 O6 O7 O8

X

Months

Car

acc

idents

No effect


Type 3. Longitudinal Type 3. Longitudinal DesignsDesigns

O1 O2 O3 O4O1 O2 O3 O4

IV: TimeIV: Time


Longitudinal Designs. Longitudinal Designs. Weaknesses.Weaknesses.

1.1. AttritionAttrition– Moving, lost motivation, mortality, etc.Moving, lost motivation, mortality, etc.– Attrition can often introduce Attrition can often introduce

systematic biassystematic bias

2.2. Researchers’ effort, time, money.Researchers’ effort, time, money.


Evaluating Quasi-Evaluating Quasi-Experimental Designs.Experimental Designs.

To conclude causality To conclude causality 1.1. The presumed causal variable The presumed causal variable

preceded the effect in time. preceded the effect in time.

2.2. The cause and the effect covary.The cause and the effect covary.

3.3. All other alternative explanations are All other alternative explanations are eliminated.eliminated.


Aggregate vs. Individual Aggregate vs. Individual TrajectoryTrajectory

Most of the information we collect tells us Most of the information we collect tells us about the average behavior of groups, but about the average behavior of groups, but not about individual patternsnot about individual patterns

Individual trajectory research explores the Individual trajectory research explores the course of a behavior or disorder within an course of a behavior or disorder within an individualindividual

Cross-Sectional design.Cross-Sectional design.

Comparison between different age Comparison between different age groups. groups.

Weaknesses:Weaknesses:1.1. Generation effectGeneration effect

2.2. No individual developmentNo individual development

No Problems

Problems

Disorder

Time1 Time2 Time3

No Problems

Problems

Disorder

Time1 Time2 Time3

Aggregate vs. IndividualAggregate vs. Individual

0% 5% 10% 15% 20% 25%

Past MonthMarijuana

Use

9th Grade8th Grade7th Grade6th Grade

Dishion et al., ‘04

Aggregate vs. IndividualAggregate vs. IndividualMarijuana Use in Last Month

0

2

4

6

8

10

12

14

grade 6 (m) grade 7 (m) grade 8 (m) grade 9 (m)

Grade

# o

f T

imes

Sm

oke

d

Moderation and MediationModeration and Mediation

Once we have found an effect: X Once we have found an effect: X Y, we Y, we can ask two questionscan ask two questions– What What mediatesmediates the effect the effect– What What moderatesmoderates the effect the effect

What What mediatesmediates the effect? the effect?

Questions of mediation are questions of Questions of mediation are questions of mechanismmechanism– HowHow does X does X Y? Through what process? Y? Through what process?

X Y

Mediator

What What mediatesmediates the effect? the effect?

Questions of mediation are questions of Questions of mediation are questions of mechanismmechanism– HowHow does X does X Y? Through what process? Y? Through what process?

Moving Ahead

Program

Employment

Work/Life Skills

What What moderatesmoderates the effect? the effect?

Questions of moderation are questions of Questions of moderation are questions of subgroupsubgroup– For whom For whom does X does X Y? Y?

X Y

ModeratorAB

+

-

What What moderatesmoderates the effect? the effect?

Questions of moderation are questions of Questions of moderation are questions of subgroupsubgroup– For whom For whom does X does X Y? Y?

Moving Ahead

Program

Employment

Stage of ChangeDenial/Pre-contemplationContemplation/Action

How Can We Really Know How Can We Really Know Causality? Causality?

Sure, science is okay, but the true Sure, science is okay, but the true measure of truth in our society?...measure of truth in our society?...

WDOT?WDOT?

WHAT DOES OPRAH THINK?WHAT DOES OPRAH THINK?

Oprah and Jenny McCarthy Oprah and Jenny McCarthy

From Oprah InterviewFrom Oprah Interview

““In recent years, the number of children In recent years, the number of children diagnosed with autism has risen from 1 in diagnosed with autism has risen from 1 in every 500 children to 1 in 150—and every 500 children to 1 in 150—and science has not discovered a reason why. science has not discovered a reason why. Jenny says she believes that childhood Jenny says she believes that childhood vaccinations may play a part. "What vaccinations may play a part. "What number will it take for people just to start number will it take for people just to start listening to what the mothers of children listening to what the mothers of children who have seen autism have been saying who have seen autism have been saying for years, which is, 'We vaccinated our for years, which is, 'We vaccinated our baby and baby and somethingsomething happened.” happened.”

From Oprah InterviewFrom Oprah Interview

““Jenny says even before Evan received his Jenny says even before Evan received his vaccines, she tried to talk to her vaccines, she tried to talk to her pediatrician about it. "Right before his pediatrician about it. "Right before his MMR shot, I said to the doctor, 'I have a MMR shot, I said to the doctor, 'I have a very bad feeling about this shot. This is very bad feeling about this shot. This is the autism shot, isn't it?' And he said, 'No, the autism shot, isn't it?' And he said, 'No, that is ridiculous. It is a mother's that is ridiculous. It is a mother's desperate attempt to blame something,' desperate attempt to blame something,' and he swore at me, and then the nurse and he swore at me, and then the nurse gave [Evan] the shot," she says. "And I gave [Evan] the shot," she says. "And I remember going, 'Oh, God, I hope he's remember going, 'Oh, God, I hope he's right.' And soon thereafter—boom—the right.' And soon thereafter—boom—the soul's gone from his eyes." soul's gone from his eyes."

Freed et al., 2009Freed et al., 2009

Online survey of parents of children up to Online survey of parents of children up to age 17age 17

1 in 4 parents agree that “some vaccines 1 in 4 parents agree that “some vaccines cause autism in healthy children”cause autism in healthy children”

Perceived LinkPerceived Link

Autism diagnoses have increased as MMR Autism diagnoses have increased as MMR vaccines have increasedvaccines have increased

Autism develops around the same age as Autism develops around the same age as the MMR vaccine is giventhe MMR vaccine is given

Autism used to be confined to upper Autism used to be confined to upper classes and did not cross class lines until classes and did not cross class lines until vaccination did sovaccination did so

Symptoms of autism mirror symptoms of Symptoms of autism mirror symptoms of mercury poisoningmercury poisoning

History of the MMR – Autism Link History of the MMR – Autism Link (reviewed by Gerber and Offit, 2009)(reviewed by Gerber and Offit, 2009)

Wakefield et al., 1998Wakefield et al., 1998– 12 Consecutively referred patients to pediatric GI 12 Consecutively referred patients to pediatric GI

department with pervasive developmental department with pervasive developmental disordersdisorders

– In 8 of these patients, parents or doctors identified In 8 of these patients, parents or doctors identified the onset of problems as occurring immediately the onset of problems as occurring immediately after MMR vaccination.after MMR vaccination.

Gerber & Offit AnalysisGerber & Offit Analysis– Because of the timing of emergence of autism, Because of the timing of emergence of autism,

and the number of children who develop autism, and the number of children who develop autism, Gerber & Offit point out that the number of children Gerber & Offit point out that the number of children Wakefield saw with autism developing shortly after Wakefield saw with autism developing shortly after MMR vaccination could occur by chance.MMR vaccination could occur by chance.

History of the MMR – Autism Link History of the MMR – Autism Link (reviewed by Gerber and Offit, 2009)(reviewed by Gerber and Offit, 2009)

Epidemiological Studies that followedEpidemiological Studies that followed– Rates of autism diagnosis did not increase Rates of autism diagnosis did not increase

significantly after introduction of MMR vaccine significantly after introduction of MMR vaccine in 1987in 1987

– No clustering of autism diagnoses around time No clustering of autism diagnoses around time of vaccinationof vaccination

– Vaccinated and unvaccinated children just as Vaccinated and unvaccinated children just as likely to develop autismlikely to develop autism

– There has been an increase in autism diagnosis There has been an increase in autism diagnosis from 1988 to 1999 though vaccination rates from 1988 to 1999 though vaccination rates have remained stable. have remained stable.

Article 2: Hobfoll et al., 2009. Trajectories of Article 2: Hobfoll et al., 2009. Trajectories of resilience, resistance, and distress during resilience, resistance, and distress during

ongoing terrorism: The case of Jews and Arabs ongoing terrorism: The case of Jews and Arabs in Israelin Israel

Research Question: Research Question: – What is the prevalence of different mental What is the prevalence of different mental

health trajectories in a population exposed health trajectories in a population exposed to ongoing terrorism and what predicts to ongoing terrorism and what predicts those trajectories? those trajectories?

This is a question that attempts to This is a question that attempts to identify psychosocial factors that identify psychosocial factors that influence mental health in a given influence mental health in a given context.context.



TrajectoriesTrajectories– Resistant (no symptoms at T1 or T2)Resistant (no symptoms at T1 or T2)– Resilient (symptoms at T1 but not T2)Resilient (symptoms at T1 but not T2)– Delayed distress (symptoms at T1 but Delayed distress (symptoms at T1 but

not T2)not T2)– Chronic distress (symptoms at both T1 Chronic distress (symptoms at both T1

and T2)and T2)



Hypotheses: Hypotheses: – Greater economic resources will distinguish resistant Greater economic resources will distinguish resistant

and resilient individuals from distressed individuals. and resilient individuals from distressed individuals. – Greater social support, less resource loss, less Greater social support, less resource loss, less

exposure, and exposure, and less less positive psychological change will positive psychological change will distinguish resistant and resilient individuals from distinguish resistant and resilient individuals from distressed individualsdistressed individuals

– Non-religious individuals will be more likely to belong Non-religious individuals will be more likely to belong to the resistant and resilient trajectories (compared to the resistant and resilient trajectories (compared to the distressed trajectory) than religious to the distressed trajectory) than religious individuals. individuals.

– Fewer resources and greater loss of resources will Fewer resources and greater loss of resources will distinguish delayed distress individuals from resistant distinguish delayed distress individuals from resistant individuals.individuals.

Article 2: Hobfoll et al., 2009. Trajectories of Article 2: Hobfoll et al., 2009. Trajectories of resilience, resistance, and distress during resilience, resistance, and distress during ongoing terrorism: The case of Jews and ongoing terrorism: The case of Jews and

Arabs in IsraelArabs in Israel Sample and Design: Sample and Design:

– Nationally representative telephone survey of Nationally representative telephone survey of adult Israelis, stratified by region (N = 1,613)adult Israelis, stratified by region (N = 1,613)

– Initial response rate of 57% at T1 and 44% of Initial response rate of 57% at T1 and 44% of the sample provided data at T2, so analyses are the sample provided data at T2, so analyses are based on one quarter of potential respondentsbased on one quarter of potential respondents

2,830

1,613 (57%)

897 drop-outs (56%)

709 T2 Data (44%)

7 insufficient data

Measures: Predictors Measures: Predictors – Demographics: Age, gender, income, education, Demographics: Age, gender, income, education,

ethnicity, religiousness, marital statusethnicity, religiousness, marital status– Terrorism exposure (# of types: 0,1,2+)Terrorism exposure (# of types: 0,1,2+)– Loss of resources (economic or psychosocial)Loss of resources (economic or psychosocial)– Post-terrorism growth (e.g., hope, intimacy, etc.)Post-terrorism growth (e.g., hope, intimacy, etc.)– Social supportSocial support

Measures: OutcomeMeasures: Outcome– PTSD symptomsPTSD symptoms– Depression symptoms Depression symptoms – 2+ PTSD or depressive symptoms used as the cut 2+ PTSD or depressive symptoms used as the cut

to classify participants as resistant or not at a to classify participants as resistant or not at a given timepointgiven timepoint


Arabs in IsraelArabs in Israel

Analysis PlanAnalysis Plan– Descriptives for each trajectoryDescriptives for each trajectory– Logistic RegressionsLogistic Regressions

– Resistant vs. DistressedResistant vs. Distressed– Gender, ethnicity, religiousness, income, education, Gender, ethnicity, religiousness, income, education,

psychosocial resource loss at T1 & T2, T2 social psychosocial resource loss at T1 & T2, T2 social supportsupport

– Resilient vs. DistressedResilient vs. Distressed– Ethnicity, income, T2 psychosocial resource loss, T2 Ethnicity, income, T2 psychosocial resource loss, T2

post-traumatic growthpost-traumatic growth

– Delayed Distress vs. ResistantDelayed Distress vs. Resistant– Education, T2 psychosocial resource lossEducation, T2 psychosocial resource loss


Arabs in IsraelArabs in Israel

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Research Methods for the Social Sciences: An Introductory Course

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