Sex<-factor(rep(c("M","F"),c(20,20)))
Age<-factor(rep( rep(LETTERS[1:5],4),rep(2,20)))
GHQ<-factor(rep(c("L","H","L","H"),rep(10,4)))
drugs<-factor(rep(c("Y","N"),20))
counts<-c(9,522,16,484,38,606,26,249,9,81,12,159,16,109,31,90,16,40,10,16,12,556,42,554,96,661,52,275,30,149,33,177,47,142,71,171,45,53,21,39)

drug.fit1<-glm(counts~Sex+Age+GHQ+drugs,family=poisson)
summary(drug.fit1)

drug.steps<-step(drug.fit1,scope~(Sex+Age+GHQ+drugs)^4)