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| From | Michael Norman Mitchell <Michael.Norman.Mitchell@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: listing groups that differ from predicted results in logit |
| Date | Thu, 25 Feb 2010 11:03:01 -0800 |
Dear DavidI am short on time, here is one thought for the significance tests of each hospital against the grand mean... you could use "deviation coding" for the hospitals. This is described at
http://www.ats.ucla.edu/stat/stata/webbooks/reg/chapter5/statareg5.htm#DEVIATIONThe admitted challenge is creating some kind of loop to create all of the deviation codes. You could also use "xi3" (see findit xi3) for automating that process. "xi3" can create the codes, but it may not play well as a prefix command to an "xt" command.
I hope that helps, Michael N. Mitchell See the Stata tidbit of the week at... http://www.MichaelNormanMitchell.com Visit me on Facebook at... http://www.facebook.com/MichaelNormanMitchell On 2010-02-25 7.02 AM, David Souther wrote:
Thanks Michael. I'm still not sure how this would let me compare among hospitals, or idcodes, because how do I know which residuals are significantly different from the rest. I found another reference that I think is similar to your approach, it talks about a LSDV (least squares dummy reg) for comparing the other dummies to the mean group effect. http://www.masil.org/documents/dummy.pdf However, it mentions that there is no straightforward way to run this model in Stata (only in SAS, limdep, R, or others). It suggests that you can use something like xtreg dv iv, fe i(groupvar) but I'm not sure if this is appropriate for my model. If I run this on the data example you gave me, it gives me slightly larger residuals but once again, I'm not sure how to translate that into a comparison of the higher vs. lower than predicted hospitals? On Wed, Feb 24, 2010 at 9:44 PM, Michael Norman Mitchell <Michael.Norman.Mitchell@gmail.com> wrote:Dear David I wonder if you might start by running this as a random intercept model. You could then look at the level two residuals to get a sense of the nature of the distribution of performance, after adjusting for the level 1 predictors. This could also give you a sense of whether there are outliers. However, I am not sure how you could translate this strategy into an actual statistical test. Here is some mock code using the "union" data file from Stata... * use the data use http://www.stata-press.com/data/r11/union.dta, clear * idcode is like your hospital id xtset idcode * union is the outcome, age and south are level 1 predictors xtreg union age south * generate the level 2 residual, naming it r2 predict r2, u * examine the residuals, for example using a histogram hist r2 I know this is not a final solution, but I hope it is a useful starting place. Michael N. Mitchell See the Stata tidbit of the week at... http://www.MichaelNormanMitchell.com Visit me on Facebook at... http://www.facebook.com/MichaelNormanMitchell On 2010-02-24 7.25 PM, David Souther wrote:Hello Statalist: I've got a dataset of individuals (id) in hospitals (hospitals) with some individual level data (indiv_var1 and indiv_var2) as well as hospital level data (hosp_var1 hosp_var2) similar to the data example below. I'd like to use the indiv* and hosp* IVs to predict the binary DV (dv). In the real dataset there are thousands of hospitals, and hundreds of individuals per hospital. What I am hoping to discover is those hospitals that have significantly higher or significantly lower than expected probabilities of the DV. So, I would like to somehow list those hospitals that are the highest/lowest. I tried running a logit with all these as IVs plus dummies for all the hospitals so that I could use predict to find the difference between the predicted and the actual values, but it drops all the dummy variables --> logit dv indiv* hosp_var1 hosp_var2 hosp_dummies* Also, I tried clogit but it said there was no variation in the groups. As an alternative, could I just run regression and get the components that go into the rvfplot (residual versus the fitted points; if that makes any sense)? Any other ideas on how to get the hospitals that are highest/lowest ?? Thanks. **data** input hosp id dv indiv_var1 indiv_var2 hosp_var1 hosp_var2 1 1 1 3 34 88 9 1 2 1 7 24 88 9 1 3 0 6 12 88 9 1 4 0 6 12 88 9 1 5 0 9 12 88 9 1 6 0 9 13 88 9 2 1 0 4 66 77 8 2 2 0 . 67 77 8 2 3 1 9 68 77 8 2 4 0 3 67 77 8 2 5 1 2 6 77 8 2 6 0 9 56 77 8 3 1 0 1 34 11 1 3 2 0 1 3 11 1 3 3 1 2 2 11 1 3 4 0 4 1 11 1 3 5 0 1 2 11 1 3 6 0 . 1 11 1 end * * 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/* * 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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