The number of cell phone minutes used by high school seniors follows a normal distribution with a mean of 500 and a standard deviation of 50.What is the probability that a student uses fewer than 400 minutes?
A)0
B)0.023
C)0.159
D)0.977

Question

Quizplus · Accepted Answer

We need to find the probability of using fewer than 400 minutes. We can standardize this value using z-score formula.

z = (x - mean) / standard deviation
z = (400 - 500) / 50
z = -2

From the standard normal distribution table, the probability of getting a z-value of -2 or less is 0.023. Therefore, the probability that a student uses fewer than 400 minutes is 0.023.

The Number of Cell Phone Minutes Used by High School