A study of a companys practice regarding the payment of invo

A study of a company\'s practice regarding the payment of invoices revealed that an invoice was paid an average of 24 days after it was received. The standard deviation equaled four days. Assuming that the distribution is normal, what percent of the invoices were paid within 18 days of receipt?

3.34%

6.68%

6.01%

5.01%

Solution

Z=(xbar-)/(/n)=(24-18)/(4/18)=6.3639, so 6.36percent of the invoices were paid within 18 days of receipt.