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From |
Jennifer Schmitt <jorg0206@umn.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: Survey design degrees of freedom help |

Date |
Thu, 03 Sep 2009 14:20:56 -0500 |

Cheers, Jennifer Andrew.Clapson@statcan.gc.ca wrote:

Jennifer, Off the top of my head, it seems to me that, if degrees of freedom can be considered roughly as the 'independent pieces of information' in the model, I suppose that given the random choosing of your clusters (villages), those 20 sub-groups are your only independent pieces of information in your sample, and anything selected out of that (sub-villages, then households) would be related, as they are in thesame cluster or PSU.BUT, given the further sampling of households out of 'sub-villages' - isn't this multi-stage sampling? Stata can handle that as well, I believe, although I haven't had cause to use it (yet). I am not sure how that would affect the degrees of freedom as Stata calculates it. -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Jennifer Schmitt Sent: September 3, 2009 1:48 PM To: statalist@hsphsun2.harvard.edu Subject: Re: st: RE: Survey design degrees of freedom helpMy sample size is 489, but I only have 20 PSU, 3 Strata so my design df= 20-3-1 (for the constant). I have a stratified, clustered sample andso my design df are based off my PSU and are thus really low. I just donot know know why this is the case (I have accepted that it is thecase), but I can't defend that without knowing why (or maybe it iswrong, but everything in the FAQ and help sections online suggest it iscorrect). Thanks.Andrew.Clapson@statcan.gc.ca wrote:Your degrees of freedom are 16?? What is your sample size? -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of JenniferSchmittSent: September 3, 2009 11:26 AM To: statalist@hsphsun2.harvard.edu Subject: st: Survey design degrees of freedom help Hello everyone,I need some important clarification about the design degrees offreedomfor stratified clustered survey analysis. I have data that wasstratified by three areas (NW, SW, and E). We randomly chose villagesfrom these three areas, then chose 5 subvillages within the villageandwithin the subvillage we chose households (the unit of interest for myanalysis). I am running logistic regressions with PSU = village,strata= area and probability weights. My design degrees of freedom are 16(PSU-strata-one for the constant term). I get that. What I do notunderstand is WHY and how to explain to others unfamiliar with STATAthat it is correct, any answers to this would be greatly appreciated.The reason this is an issue is that I want to test more than 16variables at once and obviously I can't with only 16 df. Thank you.Jennifer

-- Jennifer Schmitt PhD Candidate - Conservation Biology Program jorg0206@umn.edu * * 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/

**Follow-Ups**:**Re: st: RE: Survey design degrees of freedom help***From:*Stas Kolenikov <skolenik@gmail.com>

**References**:**RE: st: RE: Survey design degrees of freedom help***From:*<Andrew.Clapson@statcan.gc.ca>

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