Econ 102: Analysis of Economics Data: Supplemental Notes

Previous exams and supplementary problems.

Note Stata is used only from Fall 2012 onwards. Before that Excel was used.
Stata and Excel use quite different commands to obtain p-values and critical values for the t distribution.

Critcial values:
Stata command invttail( ) considers only the right tail while Excel command TINV( ) considers area in both tails.
For example, for a 95% confidence interval (or two-sided test at 5%) for t with 22 degrees of freedom use:
   Stata command invttail(22,.025)
   Excel command tinv(.05,22).

P-values:
Stata command ttail( ) considers only the right tail.
Excel command TINV( , , 1) also considers only the right tail while TINV( , , 2) considers area in both tails.

A. Colin Cameron / UC-Davis Economics / http://www.econ.ucdavis.edu/faculty/cameron