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From |
Steven Samuels <sjsamuels@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: pweights in xtiles command are doing the opposite of what I expect them to do |

Date |
Tue, 1 Feb 2011 16:53:41 -0500 |

- Michael-- I don't see a contradiction. Here's a toy example. ************************ input group x wt 1 4 2 2 5 1 1 8 2 1 9 2 2 10 1 2 12 1 2 13 1 1 20 2 2 21 1 end pctile p1=x , nq(10) pctile p2= x [pweight=wt], nq(10) bys group: sum p* x sum p* ************************ Steve Steven J. Samuels sjsamuels@gmail.com 18 Cantine's Island Saugerties NY 12477 USA Voice: 845-246-0774 Fax: 206-202-4783 On Feb 1, 2011, at 10:02 AM, Michael Boehm wrote: Dear all, I am trying to compute students' quantiles in the cognitive skill distribution using their test results reported in a survey, the Educational Longitudinal Study (ELS). The ELS oversamples individuals who are of less privileged social background, which comes with lower test scores. Therefore, individuals should be higher up in the skill distribution within the sample than compared to the whole population. If I adjust for the survey design, using the inverse probability of being selected for the survey, I however get the opposite result. For example, I would expect the mean of centil to be below centil1 and below 50. xtile centil = F1TXMSTD if G12COHRT != 0 [pweight = F2F1WT], nq(100) xtile centil1 = F1TXMSTD if G12COHRT != 0 & F2F1WT != 0 , nq(100) summarize centil centil1 Variable | Obs Mean Std. Dev. Min Max -------------+-------------------------------------------------------- centil | 12011 53.20806 28.94271 1 100 centil1 | 12011 50.48081 28.86572 1 100 What am I doing wrong here? Thanks Michael * * 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: pweights in xtiles command are doing the opposite of what I expect them to do***From:*Michael Boehm <michael.boehm1@gmail.com>

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