Assignment #7

PPol 604

Due: Thursday, 7 March 2013

Type up your answers. Give proper credit to those you work with and/or the text(s).

Solve the following problems. Show all of your work, but keep your answers concise. Highlight your (final) answer to distinguish it from your other numbers and text. Include a copy of your input (e.g. do file) or output (e.g. log file), when it is an appropriate way to show your work. However, do not include unnecessary output (i.e. no data dumps), and format any output so that it is easily readable. An appropriate time to include output is when you put your results in a table--if your results are wrong, then the grader has no idea how you came to your conclusions (i.e. give partial credit) unless you provide some output. Explanation includes statistical and substantive explanation (explain so that a statistical layperson can understand it, and so that a statistical analyst will see your erudition).

1. {20} Do Problem 4.2 in Rabe-Hesketh and Skrondal.
   • In part 4, how do the coefficients on the other covariates change (qualitatively) when the new covariates are added? Interpret the coefficients on the added covariates.
2. {20} Do Problem 4.3 in Rabe-Hesketh and Skrondal.
   • In part 2, interpret the random effects parameters as well as the coefficients.
   • After part 2, use a likelihood-ratio test to test the null hypothesis that the true random-coefficient variance is zero. Use AIC and BIC to assess whether a random intercept or random coefficient model fits the data better.
   • In part 3, graph the relationship.
3. {60} Research Project Outline:
   Turn in a combination of initial results displayed in tables and figures, including model diagnostics, along with some bullet points interpreting your results.

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