Statalist The Stata Listserver


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: RE: outreg/estimates type commands for ttest


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: outreg/estimates type commands for ttest
Date   Thu, 24 Aug 2006 12:57:09 +0100

In the case of t tests, a work-around is obtained
by noting that the results of 

regress <response> <binary variable>

are equivalent to 

ttest <response>, by(<binary variable>) 

so that -outreg- or -estout- (which I think 
you mean here rather than -estimates-) can then be 
used. 

Alternatively, a knit-it-yourself approach is 
very simple: 

. foreach v of var price-gear {
  2. qui ttest `v', by(foreign)
  3. di as txt "`v'" "{col 22}" as res %6.3f  r(t) "         "  %5.4f  r(p)
  4. }
price                -0.414         0.6802
mpg                  -3.631         0.0005
rep78                -6.016         0.0000
headroom              2.609         0.0110
trunk                 3.268         0.0017
weight                6.246         0.0000
length                5.890         0.0000
turn                  6.903         0.0000
displacement          6.597         0.0000
gear_ratio           -8.476         0.0000

The essentials: 

0. Looping over a variable list. 

1. -quietly- executing your statistical command. 

2. Picking up r() stuff (or indeed e() stuff) left in memory. 
You can -return list- or -ereturn list- or read the manual 
entry. 

3. -display-ing results, with some attention to layout and 
formats. 

The example above is the third iteration of a real example. I 
guessed lucky at r(p) and r(t) and then made changes to 
the layout and formats. 

At this point you may want to transfer to your text or 
word processor. 

Although I have mixed feelings about the program, 
I note that -makematrix- from SSC gets you there 
too:

. makematrix , from(r(p) r(t)) : ttest price-gear, by(foreign)

                       p           t
       price   .88738723   .14215113
         mpg   .00008982  -4.1688344
       rep78   8.313e-08  -6.0162381
    headroom   .00494105   2.9071556
       trunk   .00055112   3.6288312
      weight   2.047e-09   6.9268345
      length   2.461e-08   6.3182882
        turn   1.721e-10   7.5259982
displacement   3.629e-09   6.7875143
  gear_ratio   1.590e-12  -8.6552193

. makematrix results , from(r(p) r(t)) format(%6.3f) : ttest price-gear, by(foreign)

results[10,2]
                   p       t
       price   0.887   0.142
         mpg   0.000  -4.169
       rep78   0.000  -6.016
    headroom   0.005   2.907
       trunk   0.001   3.629
      weight   0.000   6.927
      length   0.000   6.318
        turn   0.000   7.526
displacement   0.000   6.788
  gear_ratio   0.000  -8.655

In this case, it is fortunate that 3 d.p. work fairly well for both p and 
t values. But then with most statistical results 3 d.p. often work well, 
although we frequently show many more places as a matter of social ritual. 

Nick 
n.j.cox@durham.ac.uk 

Nishant Dass
 
> Is anyone aware of a command (like "outreg" or "estimates")
> that I could use to tabulate "ttest" or "median" test
> results?
> 
> Although I don't think there's one, I just wanted to
> confirm.  

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index