Topic：On February 12, 1999, for only the second time in the nation's history, the U.S. Senate voted on whether to remove a President, based on impeachment articles passed by the U.S. House. Dozens of political talk shows featured analyses of why Senators may have voted the way they did, but such discourse was rarely (if ever) informed by systematic statistical analysis of the votes.
The attached dataset allows for such analysis. For each U.S. Senator, his or her votes on whether to remove President Clinton on each of the two articles of impeachment in 1999 (plus a summary variable representing each Senator's number of "guilty" votes) are provided, as well as each Senator's values on several variables that could be predictive of vote: Senator's degree of conservatism, how well Clinton did in the Senator's state in the 1996 Presidential election, the Senator's party, whether the Senator's is in his or her first term in office and the year the Senator must run for re-election.
Dataset：STATA dataset Clinton.dta（attachment）
Variable Description：
name: Name of senator
State: State (postal code)
VoteI: Vote on Article I, Perjury: 0 = Not Guilty, 1 = Guilty
VoteII: Vote on Article II, Obstruction of Justice: 0 = Not Guilty, 1 = Guilty
NVote: Total number of votes for guilty on Article I and II (0, 1 or 2).
Party: 0 = Democrat, 1 = Republican
Conserv: Senator's degree of ideological conservativism (0-100)
ClintVote: Percent of the vote Clinton received in the 1996 Presidential election in each state
year_end: The year each Senator's seat is up and he/she must run for re-election (or
retire)
first_term: First-term senator? 0 = no, 1 = yes
Research Questions
1. Which of the variables are most important to predict senators' voting behavior for his/her individual vote on Article I, Article II, and both votes jointly?
2. Which underlying econometric model(s) seem(s) to be most suitable to explain senators' voting behavior?
3. How stable are the results across the cross-section of senators? Are you able to predict the voting decisions of a sub-set of the senators given the estimates resulting from some other sub-set (out-of-sample prediction)?
4. Which role does a senator's degree of ideological conservatism play for his/her voting behavior? Analyze whether it is sensible to include this variable linearly or non-linearly (e.g., in terms of categories ranging between 0 and 100).
5. Can you finally come to the conclusion that senator’s (or at least some senator’s) voting in this impeachment was pretty predictable?

第一问，我就做regression 看p值是不是significant
后面几问就拿不定主意了。。。
求大家帮帮忙。。