Question

A study of long-distance phone calls made from General Electric Corporate Headquarters in Fairfield, Connecticut, revealed the length of the calls, in minutes, follows the normal probability distribution. The mean length of time per call was 4.3 minutes and the standard deviation was 0.50 minutes. What is the probability that calls last between 4.3 and 5.0 minutes?

Answer 1

41.92%

Explanation:

In table attached standard normal distribution curve is shown.

Data

mean, µ = 4.3 minutes

standard deviation, σ = 0.5 minutes

desired point, x = 5 minutes

x-axis, Z = (x - µ)/σ

The probability that calls last between 4.3 and 5.0 minutes is equivalent to find the area below the curve between Z = 0 and Z = (5 - 4.3)/0.5 = 1.4, which is 0.4192, or 41.92%