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st: RE: RE: save p-values from Kruskal-Wallis-test


From   "David Harrison" <david.harrison@icnarc.org>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: save p-values from Kruskal-Wallis-test
Date   Thu, 2 Jun 2005 11:35:19 +0100

The quotes are required if we need to force Stata to evaluate the contents of r(), where it otherwise would not. In this situation, they are not necessary as -display- evaluate the expression. Suppose instead we tried the following (nonsensical):

. sysuse auto
(1978 Automobile Data)

. kwallis price, by(foreign)
{output omitted}

. tabi r(df) 2 \ 3 4
'r' found where integer expected
r(7);

In this case Stata was expecting an integer, and did not evaluate r(df) to find the value 1. Now we do need the quotes:

. kwallis price, by(foreign)
{output omitted}

. tabi `r(df)' 2 \ 3 4

           |          col
       row |         1          2 |     Total
-----------+----------------------+----------
         1 |         1          2 |         3 
         2 |         3          4 |         7 
-----------+----------------------+----------
     Total |         4          6 |        10 

           Fisher's exact =                 1.000
   1-sided Fisher's exact =                 0.667

Hope this helps

David


-----Original Message-----
From: Ken Clark [mailto:Msraskc@fs1.ec.man.ac.uk]
Sent: 02 June 2005 11:23
To: statalist@hsphsun2.harvard.edu
Subject: st: RE: save p-values from Kruskal-Wallis-test


Dear All

On yesterday's list, Gerhard Schoen asked about p-values for the 
Kruskal-Wallis test.  David Harrison replied suggesting 

. display chi2tail(r(df), r(chi2))

while Kieran McCaul suggested

. display chi2tail(`r(df)', `r(chi2)')

That is, Kieran puts single quotes (presumably denoting a local 
macro) around the returned results.

My questions is simply whether, or under what circumstances, this 
second usage is better?  Would it ever give a different answer to 
the first usage?

Thanks

Ken



Ken Clark
School of Economic Studies
University of Manchester
Manchester
M13 9PL
Tel:0161-275-3679
Fax:0161-275-4812
email: ken.clark@man.ac.uk
http://www.ses.man.ac.uk/clark
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