t_test.R

# t???o ra dãy s??? id
id <- c(1:18, 1:14)
# group 1=urban 2=rural và c???n ph???i xác d???nh group là m???t "factor"
group <- c(1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
           2,2,2,2,2,2,2,2,2,2,2,2,2,2)
group <- as.factor(group)
# nh???p d??? li???u
age <- c(109,113,115,116,119,120,121,124,126,129,130,133,134,135,
         137,139,141,142,
         121,121,128,129,131,132,133,134,138,138,138,140,140,140)
height <- c(137.6,147.8,136.8,140.7,132.7,145.4,135.0,133.0,148.5,
            148.3,147.5,148.8,133.2,148.7,152.0,150.6,165.3,149.9,
            139.0,140.9,134.9,149.5,148.7,131.0,142.3,139.9,142.9,
            147.7,147.7,134.6,135.8,148.5)

# t???o m???t data frame
data <- data.frame(id, group, age, height)
attach(data)
tapply(age, group, mean)

tapply(height, group, mean)
#kiem dinh t test
t.test(age, mu=30)