Introducing Data Samples Practice Test

A grocery store chain wants to estimate the mean amount customers spend per visit at one location. Two independent random samples of 60 receipts were taken from the same month’s transactions at that location. Sample 1 had a mean of $38.50; Sample 2 had a mean of $41.20. The receipts were selected using the same random process. Why might the sample results differ?

A health clinic wants to estimate the mean waiting time (in minutes) for patients on weekday mornings. Two independent simple random samples were taken from the same set of weekday mornings during the same month. Sample 1 (n = 25) had a mean waiting time of 18.4 minutes; Sample 2 (n = 25) had a mean of 21.1 minutes. The same definition of “waiting time” was used. Why might the sample results differ?