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Re: st: How to obtain Rao-Scott chi(2) (not the F-stat) for two-way svy:tab


From   Bo MacInnis <bo@macinnis.org>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: How to obtain Rao-Scott chi(2) (not the F-stat) for two-way svy:tab
Date   Thu, 23 Dec 2010 14:25:24 -0800

Thank you very much, Steve. However, for the same 2x2 table adjusting for the sampling weight, SAS produces (done by my colleague) Rao-Scott chi2(1) = 1.34 with p = .25, but I got F-stat = 1.48 with p = .22. Our boss is not comfortable considering these two statistics identical because their values are not close enough. I was wondering if SAS might do the Rao-Scott correction differently from Stata. Thank you much for your help! Bo

On 12/23/2010 7:31 AM, Steven Samuels wrote:


Bo MacInnis-

• Rao-Scott corrected chi square = (R-1)(C-1) x (corrected F) where R= no. of Rows C = no. of Columns (Stata 11 Manual, page 130)
• In your example with R=2, C=2, the statistics are identical.
• SAS reports only the F approximation p-value, just as Stata does.

Steve

Steven J. Samuels
sjsamuels@gmail.com
18 Cantine's Island
Saugerties NY 12477
USA
Voice: 845-246-0774
Fax:    206-202-4783



On Dec 22, 2010, at 1:36 PM, Bo MacInnis wrote:

Dear Statlist mates,

I'd like to obtain the Rao-Scott chi(2) statistic for two-way svy:tab. The two-way svy:tab provides the Pearson statistics (uncorrected for design-effect as well a design effect adjusted based on Rao-Scott (1984). However, the design-based Pearson is converted into a F-stat. In my project, I'd need the chi(2) version of the Rao-Scott statistic (like what is provided in SAS, but I do not use SAS).

Here is the output from a two-way (2x2) svy:tab:
 Pearson:
   Uncorrected   chi2(1)         =    2.3737
   Design-based  F(1, 2803)      =    1.4764     P = 0.2244

Thank you very much for your help!
Bo
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