In this question, we use the data set BushIraq.dta to explore the effect of opinion about the Iraq War on the presidential election of 2004. The variables we will focus on are listed in Table 12.7.

(a) Estimate two probit models: one with only ProIraqWar02 as the independent variable and the other with all the independent variables listed in the table. Which is better? Why? Comment briefly on statistical significance.

(b) Use the model with all the independent variables and the observed-value, discrete-differences approach to calculate the effect of a one standard deviation increase in ProIraqWar02 on support for Bush.

(c) Use the model with all the independent variables listed in the table and the observed-value, discrete-differences approach to calculate the effect of an increase of one standard deviation in Party02 on support for Bush. Compare to the effect of ProIraqWar02.

(d) Use Stata's marginal effects command to calculate the marginal effects of all independent variables. Briefly comment on differences from calculations in parts (a) and (c).

(e) Use logit to run the same model.
(i) Briefly comment on patterns of statistical significance compared to probit results.
(ii) Briefly comment on coefficient values compared to probit results.
(iii) Use Stata's margins commands to calculate marginal effects of variables, and briefly comment on differences or similarities from probit results.

(f) Calculate the correlation of the fitted values from the probit and logit models. 

(g) Run a LR test on the null hypothesis that the coefficients on the three policy opinion variables (ProIraqWar02, CutRichTaxes02, Abortion00) all equal 0. Do this work manually (showing your work) and using the Stata commands for an LR test.

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TABLE 12.7 Variables for Iraq War Data Variable Bush Vote04 ProIraq War02 Party02 Bush Vote00 Description Dummy variable = 1 if person voted for President Bush in 2004 and 0 otherwise Position on Iraq War, ranges from 0 (opposed war) to 3 (favored war) Partisan affiliation, ranges from 0 for strong Democrats to 6 for strong Republicans Dummy variable = 1 if person voted for President Bush in 2000 and 0 otherwise CutRichTaxes 02 Views on cutting taxes for wealthy, ranges from 0 (oppose) to 2 (favor) Abortion00 Views on abortion, ranges from 1 (strongly oppose) to 4 (strongly support)