set.seed(123)

# Parameters for the null model:
#
n_batches = 7
n_samples = 10
m = 4
s = sqrt(0.0037)

# Make plots
#
n_plots = 2
par(mfrow=c(1, n_plots))
for( pi in 1:n_plots ){
    data = rnorm(n_batches*n_samples, mean=m, sd=s)
    DF = data.frame(value=data, grp=as.factor(rep(seq(1, n_batches), n_samples)))
    boxplot(value ~ grp, data=DF)
}

par(mfrow=c(1, 1))