Comments on Homework 2

task: simulate data from a contaminated normal compute power of t and wilcoxon tests vary contamination (p) and sample size (n)

labels?

smoothness?

comparison?

getPower <- function (n, p, N=1000) { tcounter<-wcounter<-0 for (i in 1:N){ mydata <- getData(n,p) T <- t.test(mydata, alternative=c("two.sided")) W <- wilcox.test(mydata, alternative=c("two.sided")) if (T$p.value <= 0.05){ tcounter <-tcounter+1;} if (W$p.value <= 0.05){ wcounter <-wcounter+1;} } #for loop return(list(TPower=tcounter/N, WPower=wcounter/N))}

getData<-function(n,p) { contam <- rnorm(n,3*rbinom(n,1,p),1) return(contam)}

pvector<- seq (0, 1 , by=0.1)

m<-matrix(NA, nrow=length(pvector), ncol=2)

for(i in 1:length(pvector)) { m[i,]<- as.numeric(getPower(50, pvector[i]))}

plot(pvector, m[,1], type="l", xlab="p", ylab="Power", main="n=50", lty=1)

lines(pvector, m[,2], lty=2)

legend("right", legend=c("T-test","Wilcox"), lty=c(1,2))