A sample of 100 people had a mean depression score of 85; the population mean for this depression measure is 80, with a standard deviation of 20. A different sample of 100 people had a mean score of 17 on a different depression measure; the population mean for this measure is 15, with a standard deviation of 5.

a. Convert these means to z statistics.

b. Using the z statistics, what can you say about how these two means compare to each other?