A utility company sends surveys to 200 of its customers in s…
A utility company sends surveys to 200 of its customers in such a way that 100 surveys are sent to customers who pay their bills on time, 50 surveys are sent to customers whose bills are less than 30 days late, and 50 surveys are sent to customers whose bills are more than 30 days late. A random sample is drawn from each group. Which type of sample does this represent?