Hello, I need to get a point estimate and SD for a proportion, but the subjects' data are not binary---they are proportions (of doses received). That is, I have a proportion for each subject. In the past I have analysed these data as a continuous (normal) variable, but I really don't want CIs over 100%. This seems like basic stuff, but I don't remember learning it and it's proving difficult to find (in medical statistics texts, anyway). Any pointers would be greatly appreciated! Thanks! Tanya Murphy Dept. Epidemiology McGill University
Estimates for proportions
2 messages · Tanya Murphy, Spencer Graves
1. If none of the numbers are 0 or 1, I might try a logit transformation log(p/(1-p)). Then I'd make a normal probability plot of the transformed variables to check the transformation. If that seemed OK., then I'd do the computations on logit space and back transform the result. 2. If some of the numbers are 0 or 1, I'd shrink everything from 0 and 1 using p0 = (c0+(1-2*c0)*p), then log(p0/(1-p0)). Have you considered this? hth. spencer graves
Tanya Murphy wrote:
Hello, I need to get a point estimate and SD for a proportion, but the subjects' data are not binary---they are proportions (of doses received). That is, I have a proportion for each subject. In the past I have analysed these data as a continuous (normal) variable, but I really don't want CIs over 100%. This seems like basic stuff, but I don't remember learning it and it's proving difficult to find (in medical statistics texts, anyway). Any pointers would be greatly appreciated! Thanks! Tanya Murphy Dept. Epidemiology McGill University
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