Bookmark and Share

Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, is already up and running.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: comparing coefficients using suest (same sample, same DV)

From   Christopher Baum <>
To   "" <>
Subject   Re: st: comparing coefficients using suest (same sample, same DV)
Date   Tue, 14 Aug 2012 14:12:02 +0000

On Aug 14, 2012, at 2:33 AM, Henry wrote:

> I estimate two regressions using the same sample:
> (1)	Y=b1x1+e1
> (2) 	Y=b1x1+b2x2+e2
> and would like to test the difference in b1 across the two models. I

Before trying to test for this difference, look at the t-stat on x2. If its pval is small and the correlation between (x1,x2) is nontrivial, the b1 ocefficient in the first regression is inconsistent, so why would you care how much it differs from that of the second regression?

In any case there is no need to resort to -suest- to perform this test:

sysuse auto,clear
expand 2
g secsamp = _n>74
g x1 = mpg
g x2 = trunk
g x1ss = x1 * secsamp
g x2ss = x2 * secsamp
// coefficient on x1ss is the difference in x1 when x2 is included 
reg price secsamp x1 x1ss x2ss, robust 
sca diff = _b[x1ss]
reg price x1 if !secsamp, robust
sca x1only = _b[x1]
reg price x1 x2 if secsamp, robust
sca x2only = _b[x1]
sca diff2 = x2only - x1only
di "difference from single model " diff " from separate models " diff2


Kit Baum   |   Boston College Economics & DIW Berlin   |
                             An Introduction to Stata Programming  |
  An Introduction to Modern Econometrics Using Stata  |

*   For searches and help try:

© Copyright 1996–2016 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   Site index