Dear R-ers, We are doing prediction of risk for aortic aneurysm in screened subjects based on different riskfactors. When we do the prediction on the linklevel and transform the prediction and the limits of the 95%- confidence intervall (with exponentiation and then transformation from odds to probability) we get asymmetric intervalls which seem reasonable. When we use prediction on the responselevel (which is be on the probability level) the intervalls are completely symmetric. The figures are also different. Is something wrong with the prediction or with my use of the glm program? Any help much appreciated! Sincerely yours Fredrik Lundgren This is for an individual with certain riskfactors Formation of confidence interval with linklevel (prob transforms from odds to probability) fit = -4.7513497 and se.fit = 0.2474956 point value lower limit upper limit prob(exp(-4.7513497)) prob(exp(-4.7513497-1.96*0.2474956)) prob(exp(-4.7513497+1.96*0.2474956)) Formation of confidence interval with responselevel fit = 0.008566015 and se.fit= 0.002101891 point value lower limit upper limit 0.008566015 p0.008566015-1.96*0.002101891 0.008566015+1.96*0.002101891 ######################## Fredrik Lundgren fredrik.bg.lundgren at gmail.com Engelbrektsgatan 31 582 21 Link?ping tel 013 - 47 30 117 mob 0706 - 86 39 29 Sommarhus: Ljungn?s 158 380 30 Rockneby 0480 - 650 98