If the population mean is assumed to be 20 and the sample standard deviation is 5, a score of 15 would have a Z-value of _____.
A) +1.00
B) -7.00
C) -1.00
D) +5.00

Question

Quizplus · Accepted Answer

To find the Z-score, we use the formula:

Z = (X - μ) / σ

where:
X = the raw score
μ = the population mean
σ = the population standard deviation

In this case, X = 15, μ = 20, and σ = 5.

Z = (15 - 20) / 5 = -1

Therefore, the Z-value for a score of 15 is -1. The answer is choice C.

If the Population Mean Is Assumed to Be 20 and the Sample