Date: Tue, 17 Jun 2003 21:47:20 -0400
Reply-To: Jay Weedon <jweedon@EARTHLINK.NET>
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: Jay Weedon <jweedon@EARTHLINK.NET>
Subject: Re: proc glm vs proc mixed help
Content-Type: text/plain; charset=us-ascii
On 17 Jun 03 15:16:11 GMT, raypass@ATT.NET (Ray Pass) wrote:
>I'm sending this out for a colleague. I am NOT a statistician, but I know
>where to go for help.
>> Does anyone know how to calculate the confidence interval for the
>>estimate using proc glm? I see how to calculate for the means by adding
>>to the model statement, but not for the estimate.
>> This is what I have so far:
>>title2 "GLM p-values for &var";
>>proc glm data=gmean (where=(trt in (0,1))) ;
>> class trt;
>> model l&var = trt /solution ss3 ;
>> estimate "ratio" trt -1 1;
>>It's easy in proc mixed as there is an option to do so. See below.
>>However, biostat doesn't want me to use proc mixed.
>>title2 "Proc Mixed p-values for &var";
>>proc mixed data=gmean ;
>> where trt in (0,1);
>> class trt;
>> model l&var = trt;
>> estimate "Ratio" trt -1 1 / cl ;
>> make "table" out=ratio estimate;
>>Thanks for any tips you can give me.
"Biostat" can verify the following by RTFM for PROC MIXED, but AFAIK
the method used by MIXED is the standard large-sample method:
Compute the t-statistic associated with the desired confidence level
and the error df, and multiply this by the provided SE for the
estimate. Then add/subtract this to/from the estimate value.
Estimate=4.8447 SE=1.7570 Error df=207.
2-tailed t-statistic for 207 df @ 95% CL = 1.9715.
1.9715*1.7570 = 3.4639.
CI = 4.8447 +/- 3.4639 = [ 1.3808, 8.3086 ]