Question

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 more than 350 minutes?

Answer 1

Use z-scores.

Formula:

z = (x - mean)/sd

mean = 500
sd = 50
x = 350

Substitute the values into the formula and find z. Use a z-table to determine your probability.

Answer 2

1.2857