A population has the mean of µ = 45 and standard deviation of σ = 20. Find out the z-score corresponding to each of following sample means obtained from this population (hint: employ the standard error).
A. mean = 47 for a sample of n = 4 scores
B. mean = 47 for a sample of n = 100 scores
C. mean = 40 for a sample of n = 16 scores