Explanations and Explanations and HypothesesHypotheses

Learning Objectives

How to distinguish an Acceptable Explanation from an Unacceptable Explanation.

The difference between an Independent Variable and a Dependant Variable.

How to Write a Hypothesis stating the relationship between an indep varb and a dep varb.

The importance of Rival Explanations and Alternative Hypotheses in political research.

Different Research Design used to test hypotheses.

The 2The 2ndnd goal of Political Research: goal of Political Research: To To propose and test explanations for political propose and test explanations for political

phenomena – defined by phenomena – defined by WHYWHY?? The empirical landscape is full of The empirical landscape is full of why questionswhy questions

trying to trying to explainexplain the the behaviorbehavior of people and of people and things you observe in the world.things you observe in the world.

Emp: Emp: “Why only about half of eligible voters “Why only about half of eligible voters show-up at the polls on election day?”show-up at the polls on election day?”

• ““Why do some people vote whereas others do not?”Why do some people vote whereas others do not?”

““Why” questions Why” questions have 2 elementshave 2 elements

1) Explanation in political research begins by observing a variable – a difference between subjects that we want to understand.

2) Each question implicitly requests a causal explanation for the observed difference.

Each can be recast into the form “What causes difference between subjects on this variable?”

“What causes difference between eligible voters in turnout?”

Explanation in political research involves causation.

An expiation for difference in turnout might propose that education plays a causal role.

HypothesisHypothesis HypothesisHypothesis: : a testable statement about empirical relationship a testable statement about empirical relationship

between cause and effect. between cause and effect.

An An explanationexplanation must be described in such a way that it can be must be described in such a way that it can be tested with empirical datatested with empirical data. . It must suggest a hypothesisIt must suggest a hypothesis. .

The The education turnout explanationeducation turnout explanation suggests a suggests a hypothetical hypothetical relationshiprelationship between between education education and and votingvoting. .

• If the explanation is correctIf the explanation is correct, then people with less , then people with less education will vote at lower rates than people with more education will vote at lower rates than people with more education.education.

• If the explanation is not correctIf the explanation is not correct, then level of education , then level of education

and turnout will not be empirically related.and turnout will not be empirically related.

HypothesisHypothesis A hypothesis tells us what we should find A hypothesis tells us what we should find

when we look at the data. when we look at the data.

When we examine the relationship using When we examine the relationship using empirical data, we are testing the hypothesis. empirical data, we are testing the hypothesis.

For every explanation and hypoFor every explanation and hypo there are there are alternative causesalternative causes, , rival explanationsrival explanations (under mind ability to evaluate effect of (under mind ability to evaluate effect of indep varb on dep varb --leads to indep varb on dep varb --leads to erroneous conclusions) for some erroneous conclusions) for some phenomena.phenomena.

The 3 Stages of the Explanatory Process in Political Research

1) Proposing an Explanation for a variable.

2) Stating a Hypothesis

3) Testing a Hypothesis

Schematic of the Explanatory Process = Varb Explanation Hypho Test.

The Difference Between an Independent Variable and

Dependent Variable

• Dependent Variable: the variable that represents the effect in a causal explanation.

• Independent Variable : a variable that represents the causal factor in the explanation.

FromFrom Explanation to Explanation to Hypothesis Hypothesis

A Testable Relationship is one that tells what we should find when we examine data.

A testable relationship proposes a “Hypo Comparison.” Hypothesis for relationship between gender and gun

control attitudes:

“In comparing individuals (units of analysis), those who are women will be more likely to favor a handgun ban than will those who are men (men and women are diff values of the indep var – gender – we will observe a diff in the dep varb – gun control opinion.).

Template for writing any Hypo: “In comparing [Unites of Analysis], those having [One value on the

indep Varb] will be more likely to have [One value on the Dep Varb] than will those having [A different value on the Indep Varb].”

Emp from Comparative Pol = Percent of countries voting-age pop.

“Countries using plurality systems will have fewer political parties that offer blunt choices on a large array of issues. And, turnout in those countries will be low, because voters will perceive a weak link between their votes and their impact on gov.”

This example describes several causal linkages: 1) It connects a Dep varb, Voter Turnout, with an indep varb, Type of Electoral System. 2) Also, it tells us how the 2 varbs are related. (this explanation basis for hypo).

Emp: In Comparing Countries, [Unite of Analyses] those having PR Electoral Systems [Independent

Varb] will be more likely to Have Higher Voter Turnout [Dependent Varb] than will those having Plurality Electoral Systems. [Indep Varb].

1) Independent and Dep varbs are easily identified.

2) The tendency of Hypo Relationship between them is clear.

3) The hypo tells us what to compare (PR and Plurality System).

4) Hypo tells what we should find: (Higher Turnout).

As we observed a change in the values of the indep varb, from PR Systems to Pluralityfrom PR Systems to Plurality, the Dep Varb should change from higher turnouts to lower turnouts. (Format avoid mistakes writing hypos.).

Stage 3 from Hypo to Test Test Group = composed of subjects who receive a treatment that

the researcher believes is causality linked to the Dep varb.

Control Group = composed of subjects who do not receive the treatment that the researcher believes is causality linked to the Dep varb.

A surgeon was reporting values of a Dep varb from observations that he made on a Test Group. To get an accurate assessment of the effectiveness, the researcher needs to make sure patients in both groups, Test and Control, are identical in every other way that could affect the Dep varb.

Identical or very similar in age, med hist,… for rival explanation = an alternative cause for diff values of the dep varb.

Only by making those other factors equal, by controlling them and neutralizing their effects, can we isolate the effect of indep varb on the dep varb.

Research Design. To isolate the effect of an Indep varb on a Dep varb – to neutralize

the effect of rival causes – depends on Research Design.

Research Design = Overall set of procedures for evaluating the effect of an indp varb on a dep varb.

Some are “Strong” – they control for the possible effects of all plausible rival explanations – a True Experimental DesignTrue Experimental Design.

Controlled Comparisons DesignControlled Comparisons Design = Design “Weak” – they control for some rival explanations, but they do not control for other plausible cause of the dep varb.

Natural Experiment DesignNatural Experiment Design = Researcher designs fall between these 2 poles, retaining some features of the true experimental design but remaining vulnerable to rival explanations.

True experiment = protocol in Nat sci. (not unknown in poly sci) Nat exper = more common in Soc Sci. Control compari exp = Soc Sci and Poly Sci.

True Experiment A True ExperimentTrue Experiment: 1) Allows investigator to

Manipulate Test Group and Control Group in a way that Both are Virtually Identical.

2) Then it Measures the Dependent Varb for Both Groups – called the Pre-Measurement PhasePre-Measurement Phase..

3)3) Treatment PhaseTreatment Phase = then 2 groups receive different values of the Indep Varb – usually Test Group gets “Treatment” and control group does not.

4)4) Post-Measurement PhasePost-Measurement Phase = Dep Varb is measured again for both groups.

By design – Indep Varb is the only way the groups differ, Any Observed Difference in the Dep Varb Can Any Observed Difference in the Dep Varb Can Be Attributed Directly to the Indep VarbBe Attributed Directly to the Indep Varb – not to any other cause.

True Experiment True Experiment Research Design: 2 Key

Aspects To Strength:

1) Equalizing Test and Control Group and Pre-Measuring the Dep Varb.

2) Random Assignment: Each Subject has an Equal Chance of being pickedEqual Chance of being picked for the Test or

Control Group, and It Guarantees Both It Guarantees Both Groups Groups are Virtually the Sameare Virtually the Same.

True Experiment Example of True Experiment Research Design in

Poly Sci: “Effect of Mass Media on Public Opinion.”“Effect of Mass Media on Public Opinion.”

HypothesisHypothesis:: In comparing Individuals [unite of analysis], those who are exposed to issues covered by the media will be more likely to perceive those issues as important than will those who are not exposed to issues covered by the media.

Indep Varb: Level of Media ExposureLevel of Media Exposure. Dependent Varb: Level of Perceived Impact of IssueLevel of Perceived Impact of Issue. Explanation Proposes: Media Exposure is Media Exposure is CauseCause [Indep Varb]

and Perceived Important of Media Stories is the Perceived Important of Media Stories is the EffectEffect [Dep Varb].

True Experiment Experiment Research Design imposes a Large Experiment Research Design imposes a Large

Degree of Creative ControlDegree of Creative Control; Results Obtained are Internally Valid.

Internal Validity: The Results of a Study can be Results of a Study can be GeneralizedGeneralized – findings can be applied to situations in the natural world.

True Experiment = Gold Standard in Research Procedure.

True Experiment not feasible in Poly Sci for most research questions in Poly Sci – we study units of analysis as we find them “naturally” in society and polices.

The Natural Experiment Natural Experiment DesignNatural Experiment Design:

1) The Researcher studies 2 Groups (Test and Control Group), Pre- Measures the Dep Varb for both groups,

2) Applies a “Treatment” to Test Group, and then measures the Dep Varb again for both groups.

Main distinctionMain distinction between Natural Experiment and True between Natural Experiment and True ExperimentExperiment = the subjects themselves select the group to which they will belong – Test or Control.

o All Natural Experiments are Vulnerable to Selection BiasSelection Bias – bias that occurs when the subjects who find their way into test group differ from subjects who find their way into control group – and those diff, affect the Dep Variable.

Controlled ComparisonControlled Comparison “In what ways,” other than the Indep varb, do the Test Group and the Control Group Differ?”

““How else”:How else”: In Testing the Effect of an Indep Varb on a Dep Varb we do 2 things:

1) We Make the ComparisonMake the Comparison suggested by our Hypo.

2) We Make aMake a Controlled ComparisonControlled Comparison, holding constant other Variables suggested by Rival Rival Explanations Explanations and HypoHypo.

Controlled ComparisonControlled Comparison

The “How Else” Question = Unofficial Mantra of Pol Research: It needs to be repeated It needs to be repeated every timeevery time we test a hypowe test a hypo.

“How Else, Other Than Gender, are the 2 Groups – Men and Women – Not the Same?”

This is the Logic of Inquiry in the Real World of Pol Research.

Controlled ComparisonControlled Comparison and “How Else” Mantra“How Else” Mantra define the boundaries of that world.