[R] How to solve this problem ?

[Daren Tan]

I have disabled html text editing mode, thanks to Prof. Ripley for the kind reminder. 

Given three geological devices that takes 5 readings at 4 environmental conditions (A to D). What will be the proper approach to select the most reliable device ? 

m1 <- c(73,52,49,53,83,43,58,94,53,62,75,66,41,72,70,75,57,59,85,84)
m2 <- c(31,38,30,35,36,26,27,38,22,31,24,35,36,31,38,33,32,28,33,30)
m3 <- c(65,57,36,40,36,30,40,34,37,40,33,33,37,29,37,37,30,33,40,35)

names(m1) <- rep(LETTERS[1:4], each=5)
names(m2) <- rep(LETTERS[1:4], each=5)
names(m3) <- rep(LETTERS[1:4], each=5)

Before writing this email, I have tried to compare the sd for each device at each condition, but ran into obstacle on how to formulate the null hypothesis. Alternative solution tried was ANOVA, I am unsure whether it can help, as it compares the differences in means of each group. 

Thanks