Can television inform people about public affairs? It's a tricky question because the nerds (like us) who watch public-affairs-oriented TV are pretty well informed to begin with. Therefore, political scientists Bethany Albertson and Adria Lawrence (2009) conducted a field experiment in which they randomly assigned people to treatment and control conditions. Those assigned to the treatment condition were told to watch a specific television broadcast about affirmative action and that they would be interviewed about what they had seen. Those in the control group were not told about the program but were told that they would be interviewed again later. The program they studied aired in California prior to the vote on Proposition 209, a controversial proposition relating to affirmative action. Their data (available in NewsStudy.dta) includes the variables listed in Table 9.8.

(a) Estimate a bivariate OLS model in which the information the respondent has about Proposition 209 is the dependent variable and whether the person watched the program is the independent variable. Comment on the results, especially whether and how they might be biased.

(b) Estimate the model in part (a), but now include measures of political interest, newspaper reading, and education. Are the results different? Have we defeated endogeneity?

(c) Why might the assignment variable be a good instrument for watching the program? What test or tests can we run?

(d) Estimate a 2SLS model from using assignment to the treatment group as an instrument for whether a given respondent watched the program. Use the additional independent variables from part (b). Compare the first-stage results to results in part (c). Are they similar? Are they identical? (Hint: Compare sample sizes.)

(e) What do the 2SLS results suggest about the effect of watching the program on information levels? Compare the results to those in part (b). Have we defeated endogeneity?

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TABLE 9.8 Variables for News Program Data Variable name ReadNews PoliticalInterest Education TreatmentGroup WatchProgram InformationLevel Description Political news reading habits (never = 1 to every day = 7) Interest in political affairs (not interested = 1 to very interested = 4) Education level (eighth grade or less = 1 to advanced graduate degree = 13) Assigned to watch program (treatment = 1; control = 0) Actually watched program (watched = 1, did not watch = 0) - Information about Proposition 209 prior to election (none = 1 to great deal = 4)