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I try to use proc logistic regression to estimate the probability difference between placebo and treatment group. It gives me odds ratio difference, how can I change to risk difference?
Also any difference between "risk difference" or "proportional difference" or "probability difference" between proc freq and proc logistic?
Thanks,
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Better post it at Statistical Forum ,since it is about stat . @StatDave @Rick_SAS is there .
If your data is contingency table , like
placebo treatment
good 12 23
bad 2 3
you could try
PROC FREQ;
table group*good_bad / riskdiff ;
run;
"risk difference" is for 12/(23+12) V.S. 2/(2+3) or 23/(23+12) V.S. 3/(2+3)
"proportional difference"(a.k.a odds ratio) is for 12/23 V.S. 2/3
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Better post it at Statistical Forum ,since it is about stat . @StatDave @Rick_SAS is there .
If your data is contingency table , like
placebo treatment
good 12 23
bad 2 3
you could try
PROC FREQ;
table group*good_bad / riskdiff ;
run;
"risk difference" is for 12/(23+12) V.S. 2/(2+3) or 23/(23+12) V.S. 3/(2+3)
"proportional difference"(a.k.a odds ratio) is for 12/23 V.S. 2/3
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Actually I find a very useful link. it explained everything:
http://support.sas.com/kb/37/228.html