John jay college
posted by Samantha .
A random sample of n = 9 scores is obtained from a population with μ = 50 and σ = 9. If the sample mean is M = 59, what is the zscore corresponding to the sample mean?
z = 3.00
z = 1.00
z = 9.00
cannot determine without additional information

Sample mean from a sample of size n from a normal population with mean μ and σ has parameters N(μ,σ²/n)
Since n=9, σ=9, σ²/n=9, so the sample mean ~ N(50, 3²).
Zscore=((Mμ)/σ)=(5950)/3=3