A study of a company's practice regarding the payment of invoices revealed that on the average an invoice was paid 20 days after it was received. The standard deviation equalled five days. Assuming that the distribution is normal, what percent of the invoices were paid within 15 days of receipt?
A) 15.87%
B) 37.91%
C) 34.13%
D) 86.74%
E) None of the choices are correct

Question

Quizplus · Accepted Answer

To find the percentage of invoices paid within 15 days, we calculate the z-score: z = (15 - 20) / 5 = -1. Using the standard normal distribution table, a z-score of -1 corresponds to approximately 15.87% of the data falling below this value.

A Study of a Company's Practice Regarding the Payment of Invoices