Variance
Some statistical test assume the variance of the different data sets are similar. Box plots are an easy graphical method to evulavte the variance. For example below:
A-1, A-2, and A-3 appear to be from the same population.
D-1 appears to be from a different population but has a similar variance as the A groups.
B-1 appears to be from the same population as the A samples but a much larger variance.
C-1 appears to be from a different variance and from a different population.
library(car)
setwd("c:/R")
mydata<- read.table("VarianceExampleAll.csv", header=TRUE, sep=",",)
leveneTest(EMD ~ Well, data=mydata)
mydata<- read.table("VarianceExampleSame.csv", header=TRUE, sep=",",)
leveneTest(EMD ~ Well, data=mydata)
plot(mydata, notch=TRUE)
mydata<- read.table("VarianceExampled1.csv", header=TRUE, sep=",",)
leveneTest(EMD ~ Well, data=mydata)
plot(mydata, notch=TRUE)