Question

A study of a company's practice regarding the payment of invoices revealed that an invoice was paid an average of 20 days after it was received. The standard deviation equaled five days. Assuming that the distribution is normal, what percent of the invoices were paid within 15 days of receipt?

Answer 1

15.87% of the invoices were paid within 15 days of receipt

Explanation:

An invoice was paid an average of 20 days after it was received.

Mean =
`\mu = 20`

Standard deviation =
`\sigma = 5`

Now we are supposed to find what percent of the invoices were paid within 15 days of receipt i.e.P(x<15)

Formula :
`Z=(x-\mu)/(\sigma)`

At x = 15

Substitute the values

`Z=(15-20)/(5)`

`Z=-1`

Refer the z table for p value

So, p value = 0.1587

So, 15.87% of the invoices were paid within 15 days of receipt