poisson and peritonitis
Troels Ring <tring at mail1.stofanet.dk> writes:
Dear friends. I have a very simple question. In an old paper (Vonesh,Stat Med 1990;9:263-271), the rate of peritonitis in 81 peritoneal dialysis patients is estimated. The estimated intercept and an effect for race (0,1) in a generalized linear model with poisson distribution is given. The patients are observed a different length of time but time is not in the model, so I cannot see how is accounted for that. Anyhow, the observed number of zero incidences (35) is compared to the fitted zero incidences (said to be 33.54). I would guess the way to do that was to let mm <- exp(0.00149+race*0.7888) (his intercept and effect for race) sum(dpois(0,mm)) but this doesn't yield but 25.64225 I know the times, but how could I get to the results of Vonesh without letting it have an effect ? In hope of forgiveness if I have totally misunderstood what is going on
It can only be guesswork, but one idea could be that time actually does enter but in the form exp(0.00149+race*0.7888)*time alias exp(0.00149+race*0.7888+log(time)) which is a glim with an offset. Then since the offset is known it might not be given in the results?
O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._