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 between 400 and 500 minutes?
A)0.4773
B)0.05228
C)0.0228
D)0.9773
E)None of the above

Question

Quizplus · Accepted Answer

The probability of using between 400 and 500 minutes is the area under the normal distribution curve between these two values. This is calculated as the difference between the cumulative probability at 500 minutes and at 400 minutes. The Z-score for 500 is 0, and for 400 is -2. The cumulative probability for Z = 0 is 0.5, and for Z = -2 is approximately 0.0228. The difference is 0.4772, which is closest to 0.4773.

The Number of Cell Phone Minutes Used by High School