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From |
"Austin Nichols" <[email protected]> |

To |
[email protected] |

Subject |
Re: st: --svy & --pweights: problems for median, graphs & regression |

Date |
Thu, 11 Sep 2008 10:19:33 -0400 |

[email protected] -- On (b): Note also that -eqprhistogram- on SSC allows aweights, as does -tabulate-, and for proportion in each category, aweights are the same as pweights. You can make your own histogram with pweights/aweights with -collapse- as well: sysuse auto, clear ren rep78 category preserve g one=1 collapse (sum) one [pw=wei], by(category) keep if category<. g s=sum(one) egen Fraction=max(s) replace Fraction=one/Fraction sc Fraction category, recast(bar) l restore tab category [aw=wei] In fact, I can't see why Stata does not allow aweights (or even pweights) in -histogram- (I believe that was a Wishes/Grumbles item). On Thu, Sep 11, 2008 at 3:07 AM, Steven Samuels <[email protected]> wrote: > Hafida > > > > a. Look at -help- for -pctile- and -_pctile-. These take pweights > > b. -histogram- will take fweights, but not pweights: See > http://www.stata.com/statalist/archive/2007-10/msg00327.html and preceding > messages in the thread. > > c. -svy: reg- automatically computes standard errors that are robust to > heteroskedasticity. Homogeneity of variance is not an assumption for survey > tests of means or regression coefficients. > > d. See: http://www.stata.com/statalist/archive/2007-12/msg00621.html to > compute an adjusted R-square with survey data. You should consider other > measures of fit, such as -linktest-. > > e. No--not if you want to believe the standard errors and tests. However > you might be able to test hypotheses about single-outcome survey regressions > with -suest-. > > To use the survey-enabled programs like -svy: reg- for inference > (hypothesis, confidence intervals, standard errors) you must first -svyset- > your data. -svyset- will allow you to account for the entire sampling > design, not just weighting. > > > For future reference the appropriate way to refer to Stata commands in the > list is with hyphens around them" "-manova-" , not "--manova" > > > -Steve > > On Sep 11, 2008, at 12:59 AM, [email protected] > wrote: > >> Hi all, >> >> I have 4 continuous DVs (quality of life domains of SF-36: GH, PF, MH, SF) >> which are moderately inter-correlated (0.5) and two of them have skewed >> distributions. I originally intended to use --manova & --mvreg until lately >> when I realised that I'm using a dataset from a survey with over-sampling >> for participants living in remote areas. The dataset had had a weighted >> variable already so have to take this into account. To some extent, this had >> affected the statistical method I'd like to use previously. So far, I've >> performed a separate analysis for each DV as I have no idea on how to apply >> --svy nor --pw to --manova and --mvreg. >> >> Some of my concerns are: >> a. I need descriptives other than mean & proportion, particularly for >> skewed DVs which I think median or percentiles is more appropriate. While >> --svy does not support this, is there a way to get the estimates? >> b. How to create histogram for weighted mean DV as this will help get a >> sense if assumption for normality for an OLS regression is met? >> c. When using --regress with --svy to get ANOVA, how is homogeneity of >> variance assessed? >> d. I noticed that there is no adjusted R-squared when using --svy, so is >> it appropriate to build a model using R-squared instead? >> e. Lastly, if it's not impractical at all, is it still possible to run >> --mvreg and take weights into account? * * 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/

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