A frequency distribution has a mean of 100 and a standard deviation of 20. The class limits for one class are 50 up to 60. What are the standard normal z-statistics for the class limits?
A)−20 and 20
B)−2.5 and −2.0
C)2.0 and 2.5
D)−50 and −40

Question

Quizplus · Accepted Answer

To calculate the z-statistics we use the formula:

z = (x - μ) / σ

For the lower class limit x = 50, μ = 100, and σ = 20, we get:

z = (50 - 100) / 20 = -2.5

For the upper class limit x = 60, μ = 100, and σ = 20, we get:

z = (60 - 100) / 20 = -2.0

Therefore, the standard normal z-statistics for the class limits are -2.5 and -2.0.

A Frequency Distribution Has a Mean of 100 and a Standard