Question

In a large sample of customer accounts, a utility company determined that the average number of days between when a bill was sent out and when the payment was made is 11 with a standard deviation of 13 days. Assume the data to be approximately bell-shaped. Approximately 95% of all customer accounts have the average number of days between two values A and B. What is the value of B? Write only a number as your answer.

Answer 1

Using empirical (68-95-99.7) rule,

Approximately, 95% of the data falls between 2 standard deviation of the mean.

That is 95% data falls between - 2 and + 2

Given,

95% data falls between A and B,

so A = - 2 and B = + 2

B = 11 + 2 * 13

= 37