课上的作业。没有基础，于是一片茫然。

附件里面是.dta文件和作业要求

我对这个没想法了。

d) Predict conditional probability for single outcome within group accord-
ing to the third speci¯cation. Within group the choice variable which
has the largest predicted probability is the predicted outcome. Tabulate
predicted choice outcomes and report percentage of correct predictions
for each outcome.

还有，请仗义的XDJM帮我看看，我前面想的对不对

use D:\TRAVEL

a)Descriptive statistics. 3 P
² Report the proportion of choices.
² Report the descriptive statistics of individual specific variables.
² Report the descriptive statistics of the alternative-specific variables
by the choice outcome.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

proportion air train bus car
summarize choice mode costs transt hinc pers air train bus car
sort choice
by choice:summarize mode costs transt hinc pers

b)Estimate three di®erent conditional logit specifications.
² Use for the first specification only attribute specific information.
² Let the second specification additionally contain attribute specific
intercept terms.
² The third specification should contain attribute specific and indi-
vidual specific variables.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

logit choice mode costs transt hinc pers, group(id)
[这里非常非常茫然T___T]

c) Display odds ratio using relevant command in STATA. Interpret the
coe±cients of the most general specification. What do the estimated
coe±cients tell us about the e®ect of the corresponding X variable on
the choice probabilities?
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

logistic air transt

[在网上查的关于odds ratio的意义和做法，http://www.ats.ucla.edu/stat/Stata/library/odds_ratio_logistic.htm
更复杂的就不清楚了]

帮帮我吧……