Kizspy | Question: 34
(Choose 1 answer)
The compressive strength of concrete is normally distributed with mean =1200 psi and standard deviation=30.A random sample of n-9 specimens will have a sample mean diameter that falls in the interval from 1011 psi to 1230 psi. What is the standard error of the sample mean?
Α. 400/3
B. None of the others
C. 40
D. 30/9
Ε. 10
