Don <- read.table("https://husson.github.io/livre_exo/chap3_ex4.csv", header = TRUE, sep=";", encoding = "latin1", stringsAsFactors = TRUE) by(Don[,"Distance"],Don[,"Sexe"],mean) by(Don[,"Distance"],Don[,"Sexe"],sd) ## Question 2 et 3 by(Don[,"Distance"],Don[,"Sexe"],t.test,mu=12,conf.level=0.80) by(Don[,"Distance"],Don[,"Sexe"],t.test,mu=12,conf.level=0.95) by(Don[,"Distance"],Don[,"Sexe"],t.test,mu=12,conf.level=0.99)