trIn Proc Genmod, I chose the logit function as a link function. But I did not specifiy the option for distribution. Under this condition, what distribution will be used? Normal distrubtion is a defualt in this case? ... View more

I am trying to estimate IRT a (item discrimination) and b (item difficulty) parameters from the probability of correct response (=p+ values) conditioned on each of the 8 theta points. Someone told me that I have to use logit function to get the "a" and "b" parameters. So I ran the proc Genmod procedure as shown below, but the result looks not right. Data temp; input theta p; card; -3.0 .001 -2.5 .015 --- 2.5 .950 3.0 .998 ;;;; run; proc genmod data=temp; model p=theta / link=logit, dist=poi; run; Would you let me know what SAS function I have to use to get the correct "a" and "b" parameters? Thanks! ... View more