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From |
"Martin Weiss" <martin.weiss1@gmx.de> |

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

Subject |
AW: st: test difference in quintiles |

Date |
Wed, 10 Jun 2009 17:44:39 +0200 |

<> Try: ************* clear* set obs 10000 capt prog drop differ gen x= rnormal() /*no systematic difference btw groups THIS IS equivalent to your Y and Z conditions*/ gen condition=runiform()<0.5 pr differ, rclass vers 10.1 qui su x if /* */ condition==0,/* */ det loc first=r(p5) qui su x if /* */ condition==1,/* */ det ret sca diff = r(p5)-`first' end bs diff=r(diff), /* */ reps(200): differ ************* HTH Martin -----Ursprüngliche Nachricht----- Von: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Susanne Neckermann Gesendet: Mittwoch, 10. Juni 2009 17:38 An: statalist@hsphsun2.harvard.edu Betreff: Re: st: test difference in quintiles Dear T thank you very much for the message!! I am a real beginner with Stata and I have to admit that I do not quite understand how to transfer the code to my case. I have a variable X that I observe under two conditions Y and Z. I want to see if the fifth percentile of variable X in condition Y is different from the fifth percentile of X in condition Z. Thank you so much for your input!! Best Susanne On 10-Jun-09, at 5:26 PM, Tirthankar Chakravarty wrote: > <> > > This is a variation of previous advice: > http://www.stata.com/statalist/archive/2009-05/msg00311.html > > I believe you want to test the significance of the difference of the > 5th percentile for two variables using a bootstrap. If this is the > case, then the code below applies: > > /* Bootstrap the difference of percentiles */ > clear > webuse nlswork, clear > keep idcode year ttl_exp > reshape wide ttl_exp, i(idcode) j(year) > > cap prog drop pctile_bs > program define pctile_bs, rclass > version 10 > syntax varlist(max=2 min=2) [if] [in] > marksample touse > tokenize `varlist' > local first `1' > macro shift > local second `*' > _pctile `first' if `touse', percentiles(5) > scalar pc1 = r(r1) > _pctile `second' if `touse', percentiles(5) > scalar pc2 = r(r1) > return scalar dpc = pc1-pc2 > ereturn post, esample(`touse') > end > bootstrap Dpc = r(dpc), reps(2000) dots: pctile_bs ttl_exp68 > ttl_exp69 > /* End */ > > Please also see the reference about pivotal statistics in a bootstrap > from the previous message. > > T > > > On Wed, Jun 10, 2009 at 3:57 PM, Susanne > Neckermann<sneckermann@iew.uzh.ch> wrote: >> Hi! >> >> I want to test whether the difference in the fifth percentile of two >> distributions is significant. >> In principle, this test should be similar to the "median" (thats >> the name of >> the command) test already implemented in Stata, but unfortunately I >> cannot >> program .ado files and I could not find a user-written procedure. >> Any idea how to go about this? >> P.S. the number of observations in the fifth percentile is pretty low >> (around 6), so one might have to use something with bootstrap or >> permutations. >> >> Thank you so much in advance >> susanne >> >> >> >> * >> * 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/ >> > > > > -- > To every ω-consistent recursive class κ of formulae there correspond > recursive class signs r, such that neither v Gen r nor Neg(v Gen r) > belongs to Flg(κ) (where v is the free variable of r). > > * > * 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/ * * 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**:**Re: st: Need to Title a Second Y-Axis...***From:*Maarten buis <maartenbuis@yahoo.co.uk>

**RE: st: Need to Title a Second Y-Axis...***From:*"Ploutz-Snyder, Robert (JSC-SK)[USRA]" <robert.ploutz-snyder-1@nasa.gov>

**st: test difference in quintiles***From:*Susanne Neckermann <sneckermann@iew.uzh.ch>

**Re: st: test difference in quintiles***From:*Tirthankar Chakravarty <tirthankar.chakravarty@gmail.com>

**Re: st: test difference in quintiles***From:*Susanne Neckermann <sneckermann@iew.uzh.ch>

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