I have very little experience working with weights, so please correct me if my understanding is wrong.
I'm trying to create a summary table of unadjusted rates of quality of care between the TM and MA groups. I was able to produce a table with Proc Ttest and ODS. However, the survey uses a complex design. I need to add a weight variable and, it appears, replicate weight variables. Unfortunately, Proc Ttest can accommodate a weight variable but not replicate weights.
Just to experiment, I tried running Proc Ttest with the weight variable, and the sig score for the variables improved. That confuses me, because the study documentation says "To permit the calculation of random errors due to sampling, a series of replicate weights were computed. Unless the complex nature is taken into account, estimates of the variance of a survey statistic may be biased downward." In other words, not using weights means underestimating the variance. And if the true variance is actually higher, shouldn't that reduce the significance level? One particular variable I looked at has a probt score of 0.0158 when unweighted, and 0.0025 when weighted.
Based on what I found in the study documentation, I'm trying to use Proc Surveyfreq instead. However, this is confusing me as well. The Pr > ChiSq score is now <.0001 for every variable, even those that were not significant when I used Proc Ttest.
Here is the code, with sample data and Proc TTest commented out. I'm only including 1 of the replicate weights here, but there are actually 100 of them:
data have;
infile datalines dsd dlm=',' truncover;
input ACC_HCTROUBL_r ACC_HCDELAY_r ADRD_group TM_group
PUFFWGT PUFF001;
datalines;
3,1,1,0,1310.792231,1957.576268
2,1,1,1,10621.60998,18588.46812
3,2,1,1,3042.093381,5484.728615
3,2,1,1,3166.358963,5497.289892
3,2,1,0,1481.272986,432.6313548
2,2,1,1,6147.605583,9371.965632
2,1,1,1,14001.79093,16689.25322
3,1,1,1,2035.685768,530.211881
2,1,1,1,6356.258972,1899.874476
3,2,1,0,1487.104781,2018.636444
2,1,1,0,5002.553584,1364.125425
2,2,1,1,2493.79145,4039.542597
3,2,1,0,2260.257377,3495.675613
2,2,0,1,9358.048737,2835.543292
3,2,1,1,2978.506348,4932.378916
3,2,1,1,2794.906054,5118.430973
3,1,1,0,1663.418821,519.7549258
3,2,1,0,2083.459361,3067.105973
2,1,1,0,5106.785048,8672.202644
3,1,1,1,3447.574748,854.6276748
3,2,1,1,2819.233426,899.849234
3,2,1,0,4067.38684,6463.15598
3,2,1,1,1249.96647,2053.666234
3,2,1,1,1730.237908,3058.307502
3,2,1,1,4932.936202,1479.55826
; RUN;
/*PROC TTEST plots=none data=have;
CLASS TM_group;
VAR ACC_HCTROUBL_r ACC_HCDELAY_r;
WEIGHT PUFFWGT;
REPWEIGHT PUFF001; /*REPWEIGHT PUFF001-PUFF100;*/
RUN;*/
PROC SURVEYFREQ data=have VARMETHOD = brr (fay=.30);
TABLE ACC_HCTROUBL_r ACC_HCDELAY_r * TM_group / row chisq lrchisq;
WEIGHT PUFFWGT;
REPWEIGHT PUFF001; /*REPWEIGHT PUFF001-PUFF100;*/
WHERE ADRD_group ^= 1;
RUN;
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