# R course, Thursday 09/03/2017 # Basic statistics in R # Scripts used in class # Function t.test ?t.test # Example 1 mars <- read.table("data/mars.txt",header=TRUE) head(mars) t.test(mars$size[mars$color=="green"],mars$size[mars$color=="blue"]) # Example 2 data(shoes,package="MASS") head(shoes) t.test(shoes$A,shoes$B,paired=TRUE) # Power of a test mean(mars$size[mars$color=="green"]) sd(mars$size[mars$color=="green"]) ?power.t.test power.t.test(n=NULL, delta=5, sd=8, sig.level=0.005,power=0.9, type="one.sample", alternative="two.sided")