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From |
"Rajesh Tharyan" <R.Tharyan@exeter.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: different result each time |

Date |
Thu, 25 Sep 2008 10:50:02 +0100 |

Hi Eva, Thanks .. that was exactly the problem! I was doing a merge way upstream before the section where I run the t-tests, I was doing select all and running the do file and that was causing the problem. I think with the stable option that problem seems to have gone away. Thanks Rajesh Tel: +44 (0)1392 262544 Fax: +44 (0)1392 262475 E-mail: r.tharyan@exeter.ac.uk -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Eva Poen Sent: 25 September 2008 10:12 To: statalist@hsphsun2.harvard.edu Subject: Re: st: different result each time Rajesh, I find this puzzling. The usual reason for differing results is that some of the code requires random numbers, and the seed had not been set (e.g. -set seed 123-). However, there is nothing random in your code. The only thing I can think of is that there is a random element happening before the loop that you don't show us. Do you -sort- your data, and then use -in-? E.g. sort thisvar thatvar keep in 1/200 foreach i in 1 2 3 4 7 0 { ... } If your -sort- statement does not uniquely identify observations, you will get a different set of 200 observations each time you run the loop. This example shows it for the auto data: *** forvalues x = 1/5 { sysuse auto, clear gen id = _n sort mpg list id in 6/10 } *** Hope this helps, Eva 2008/9/25 Rajesh Tharyan <R.Tharyan@exeter.ac.uk>: > Hi all, > > I am using the following code to do a bunch of t-tests and output the > results to excel > > foreach i in 1 2 3 5 7 9 { > ttest winar`i' if type=="C", by(class) > scalar m1`i'=`r(mu_1)' > scalar m2`i'=`r(mu_2)' > scalar mdiff`i'=(`r(mu_1)'-`r(mu_2)') > scalar t`i'=r(t) > scalar p`i'=r(p) > } > matrix C = > (m11,m12,m13,m15,m17,m19\m21,m22,m23,m25,m27,m29\mdiff1,mdiff2,mdiff3,mdiff5 > ,mdiff7,mdiff9\t1,t2,t3,t5,t7,t9\p1,p2,p3,p5,p7,p9) > matrix rownames C= PB PS PB-PS t-stats p-val > matrix colnames C= (per1) (per2) (per3) (per4) (per5) (per6) > mat li C > xml_tab C,append > clear all > > Each time I run this I get different results. See below ( only the first row > of matrix is shown) > > Run1 > PB 0.234 0.109 0.027 -0.020 0.006 0.186 > > Run2. > PB .22601096 .10431468 .02967896 -.00025647 .02184916 .21296798 > > And so on. Why? Any thoughts > > Regards > rajesh * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: testing for endogeneity with cluster()***From:*"ritashree chakrabarti" <hirup01@gmail.com>

**st: RE: testing for endogeneity with cluster()***From:*"Schaffer, Mark E" <M.E.Schaffer@hw.ac.uk>

**Re: st: different result each time***From:*"Eva Poen" <eva.poen@gmail.com>

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