a) A financial officer for a company wants to estimate the percent of accounts receivable that are

more than 30 days overdue. He surveys 200 accounts and finds 142 are more than 30 days overdue.

Compute a 90% confidence interval for the true proportion of accounts receivable that are more than

30 days overdue.

b) A commuter travels many kilometres to work each morning. She has timed this trip 8 times during

the last month to record the following sample (in minutes) showing the time required to make the trip

each time:

48, 47, 43, 49, 40, 39, 43, 44

Construct a 95% confidence interval to estimate the population mean time the commuter takes

travelling to work in the morning.