The SEC requires companies to file annual reports concerning their financial status. It is impossible to audit

Question:

The SEC requires companies to file annual reports concerning their financial status. It is impossible to audit every account receivable. Suppose an auditor audits a random sample of 49 invoices and finds a sample average of $128 and a sample standard deviation of $53.
a. Find a 99% confidence interval for the mean size of an invoice. Does your answer require the sizes of the invoices to be normally distributed?
b. How large a sample is required for you to be 99% sure that the estimate of the mean invoice size is accurate within $5?

Accounts Receivable
Accounts receivables are debts owed to your company, usually from sales on credit. Accounts receivable is business asset, the sum of the money owed to you by customers who haven’t paid.The standard procedure in business-to-business sales is that...