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From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: st: Obtaining descriptive Stats on matched samples Pre & Post |

Date |
Mon, 11 Apr 2011 07:59:43 +0100 |

Suppose your variables include -id time q38- and you -tsset id time-. Then the individuals who answered at both times are identified by by id (time) : gen OK = !missing(q38) & !missing(q38[3-_n]) as for the first time _n is 1 and 3 - _n is 2 and for the second time _n is 2 and 3 - _n is 1. or by bysort id : gen nmissing = sum(missing(q38)) by id : replace nmissing = nmissing[_N] ... if nmissing == 0 However, it would seem that you might want information only on individuals who asked all questions at all times, for which you might well start off with something more like egen nmissing = rowmiss(q1-q50) bysort id : replace nmissing = sum(nmissing) by id : replace nmissing = nmissing[_N] ... if nmissing == 0 Nick On Mon, Apr 11, 2011 at 7:02 AM, Clifton Chow <clifton_chow@post.harvard.edu> wrote: > I have an unabalanced panel dataset from an identical survey given at 2 interview periods. There are 30-50 questions given in the survey and for each question, some individuals answered at Tiime 1 but not at Time 2 and vice-versa. How can I obtain summary statistics on each question that was answered by individuals at both interview periods? In other words, I need to calculate a Pre and Post mean & variance for each survey item in which there was no missing value for that item pre and post for the ssample? For example, Question 38 had N=72/95 who responded in Time 1 and N=57/95 who responded in Time 2, but some of the 57 who responded in Time 2 did not do so in Time 1. * * 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: st: Obtaining descriptive Stats on matched samples Pre & Post***From:*"Clifton Chow" <clifton_chow@post.harvard.edu>

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