A normally distributed set of scores has a μ = 500 and σ = 100. What proportion of scores is equal to or less than 400?
A).1587
B).5000
C).3413
D).8413

Question

Quizplus · Accepted Answer

To find the proportion of scores equal to or less than 400, we calculate the z-score: $z = \frac{X - \mu}{\sigma} = \frac{400 - 500}{100} = -1$. Looking up a z-score of -1 in a standard normal distribution table gives us a proportion of 0.1587, or 15.87%.

A Normally Distributed Set of Scores Has a μ =