B = 10^5;  n = 10;  mu = 1000;  sg = 1
 DTA = matrix(rnorm(B*n, mu, sg), nrow=B)  # each row a sample of size n
 a = rowMeans(DTA)      # vector of B sample means
 s = apply(DTA, 1, sd)  # vector of B sample SDs
 rel.er.a = abs(a - mu)/mu;  mean(rel.er.a)
 ## 0.0002509101  # estimated MAE(sample mean)
 rel.er.s = abs(s - sg)/sg;  mean(rel.er.s)
 ## 0.1880363     # estimated MAE(sample SD)