面板数据分析Mediation Moderation1

1、The Importance of Testing Mediation and Moderation,Jon A. Krosnick Departments of Communication, Political Science, and Psychology Stanford University,Outline for Today,Introduction: Defining and Testing Mediation and Moderation Example: News Media Priming Example: Public Learning About Policy Issue

2、s,Introduction,The Audience Participation Portion of Todays Show,What is a moderator?- Definition- Example of moderation What is a mediator?- Definition- Example of mediation,Moderator A variable that changes the impact of one variable on another. PredictorOutcome,Moderator,Testing a Moderator Hypot

3、hesis,Dont Presume Linearity,Mediator The mechanism by which one variable affects another variable,Testing Mediation,Step 1: IVDV Step 2: IVMediator Step 3: MediatorDV Step 4: Effect of IV on DV is significantly reduced by controlling for the mediator: Sobel (1982) test (/preacher/s

4、obel/sobel.htm) Goodman (1960) test On the exact variance of products. Journal of the American Statistical Association, 55, 708-713.,First Example:,News Media Priming,News Media Priming,News media attention to an issue increases the impact of performance assessments in the domain on overall presiden

5、tial evaluations.,Presidential Performance Handling Unemployment,Overall Presidential Performance,Media Attention to Unemployment,Mediation of Moderation,Unemployment Presidential Performance,Overall Presidential Performance,Media Attention to Unemployment,Accessibility of Unemployment Performance A

6、ssessment,Unemployment Story,Unemployment Attitudes,Unemployment,Study Design,Pre-exposure questionnaire - 5 non-political TV news stories 2 stories on either: Crime Pollution Unemployment Post-exposure questionnaire,Measures,Overall presidential performance Presidential performance handling: Crime

7、Pollution Unemployment Accessibility (response latency) Political knowledge Trust in the news media,Moderation of Mediation of Moderation!,Not Mere Accessibility Persuasion?,Unemployment Presidential Performance,Overall Presidential Performance,Media Attention to Unemployment,Belief that Media Perso

8、nnel Believe the Issue is Important for the Nation,Trust in the Media,Political Knowledge,Belief that the Issue is Important for the Nation,Conclusion,Understanding moderation and mediation increase confidence in the causality claim Understanding mediation changed the political character of the effe

9、ct (not victims of the architecture of the mind) Understanding moderation changed the normative spin of the effect (not nave people who lack political expertise people choose to be influenced),Example Two:,How Do People Learn About Politics?,October 13, 1988 Presidential Debate George H. W. Bush vs.

10、 Michael Dukakis,Day Before: 134 people interviewed Day After: 63 reinterviewed - Cued Recall - Recognition Memory - Attitude Importance,Analysis: Hierarchical Linear Modeling,Participant TaxesCapital Defense PunishmentSpending CR RMCR RMCRRM,Effect of Importance on Knowledge,b=.46 SE=.23 p.05 N=366

11、,The Usual Approach,Stop There. Smile. Fold Up Tent. Go Home.,.11*,.04,.31*,.44,Laboratory Experiment Conditions Unpaced,A woman should have the right to obtain an abortion if she so chooses. The death penalty is an acceptable punishment for convicted murderers. We should build more nuclear power pl

12、ants to provide an alternative source of energy. The U.S. should send more troops to Saudi Arabia to oppose Iraqs invasion of Kuwait. In order to protect American jobs, we need more restrictions on the number of goods imported.,Candidate A,Laboratory Experiment Conditions Unpaced Paced,“You will hav

13、e 20 seconds to read five statements made by each candidate. After 20 seconds, the statements will disappear, so read as quickly as you can.”,Laboratory Experiment Conditions Unpaced Paced Elaboration Time,“You will have 20 seconds to read five statements made by each candidate. After 20 seconds, th

14、e statements will disappear, so read as quickly as you can. Once the statements disappear, you will have 45 seconds to think about what you read.”,Laboratory Experiment Conditions Unpaced Paced Elaboration Time Topic Labels,A woman should have the right to obtain an abortion if she so chooses. The d

15、eath penalty is an acceptable punishment for convicted murderers. We should build more nuclear power plants to provide an alternative source of energy. The U.S. should send more troops to Saudi Arabia to oppose Iraqs invasion of Kuwait. In order to protect American jobs, we need more restrictions on

16、 the number of goods imported.,Candidate A,Abortion,Death Penalty,Nuclear Power,Iraq,Imports,Measures,Free Recall Recognition Memory Attitude Importance,Alternative Hypothesis,Actual Knowledge Volume,Perceived Knowledge Volume,Attitude Importance,.37*,.27*,.38*,.55*,.04,.00,Conclusions,You can test

17、mediation with panel data You can test mediation via moderation manipulations in the lab You can test mediation with cross-sectional data with instrumental variables and 2SLS,Broader Conclusion,Test mediation (and moderation)! Two examples where this was not done: Valentino, N. A., Hutchings, V. L., &