Introduction to Statistical Methods

Analysis of Variance

arith <- read.csv ("arith.csv", header = T, stringsAsFactors = TRUE) 

# have a look at the data
arith

##    scores methods
## 1      48      m1
## 2      73      m1
## 3      51      m1
## 4      65      m1
## 5      87      m1
## 6      55      m2
## 7      85      m2
## 8      70      m2
## 9      69      m2
## 10     90      m2
## 11     84      m3
## 12     68      m3
## 13     95      m3
## 14     74      m3
## 15     67      m3

plot (arith$scores, col = arith$methods)

# do anova
arith.aov <- aov ( scores ~ methods, data = arith)
# look at the result
summary (arith.aov) 

##             Df Sum Sq Mean Sq F value Pr(>F)
## methods      2  432.1   216.1   1.093  0.366
## Residuals   12 2372.8   197.7