A sample of 16 items had a mean of 30.

Question

A sample of 16 items had a mean of 30. It is assumed that the population mean is 35 and the population standard deviation is 7. What is the z-value associated with this sample mean?
a.
-2.86
b.
-0.71
c.
0.71
d.
2.86

Answer 1

z value formula

 

(observed mean - expected mean) / (standard deviation / square root of the number of samples)

 

(30-35) / (7/√16)

 

-5 / (7/4)

 

z = -2.857 ≈ -2.86