Question

question 5
the number of days (x) after mailout it takes a utility company to receive payment for a customers bill is a normal random variable with a mean of 31 days and a standard deviation of 6 days.
the probability is 0.99 that a bill will be received between which of the following number of days?
a. (13, 49)
b. (19, 43)
c. (25, 37)

Explanation:

Step1: Recall empirical rule

For normal distribution, about 99.7% data lies within 3 standard - deviations of the mean.

Step2: Calculate lower bound

$31−3\times6 = 13$

Step3: Calculate upper bound

$31 + 3\times6=49$

Answer:

A. (13, 49)