N <- 34
post_test <- 
c(81.6, 101.2, 66.4, 96.2, 101.3, 108.9, 114.6, 111.7, 97.3, 96.5,
94.9, 104.8, 104.5, 108.3, 101.9, 100.1, 91.7, 92.5, 94.4, 101.3, 102.2, 100.6,
113.8, 114.3, 87.9, 105.6, 102.5, 93.6, 109.2, 111.2, 106.4, 110.6, 112.1,
113.3)
pre_test <- 
c(55.1, 73.1, 51.4, 62.3, 69.7, 70.9, 82.5, 83.9, 69.8, 69.2, 75.1,
68.2, 83.5, 71.7, 80.3, 76.6, 70.1, 60.9, 72.3, 78.6, 77.4, 71.8, 93, 97.7,
65.7, 80.4, 75.6, 68.4, 83.3, 93.7, 87.3, 95.2, 80.4, 85.4)
grade <- 
c(2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2)
treatment <- 
c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1)
supp <- 
c(0, 0, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 1, 1, 1,
0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1)