3 An electrical goods chain is having a New Year sale of refrigerators. The number of refrigerators sold during this sale at a sample of 10 stores was 80 110 0 40 70 80 100 50 80 30 a Is there evidence that an average of more than 50 refrigerators per store was sold during this sale? Use a = 0.05.

b What assumption is necessary to perform this test?