An analyst in the publishing industry wants to find out whether the cost of a newspaper advertisement of a given size is about the same in four large newspaper groups. Random samples of seven newspapers from each group are selected, and the cost of an ad is recorded. The data follow (in dollars). Do you believe that there are differences in the price of an ad across the four groups?

Group A: 57, 65, 50, 45, 70, 62, 48

Group B: 72, 81, 64, 55, 90, 38, 75

Group C: 35, 42, 58, 59, 46, 60, 61

Group D: 73, 85, 92, 68, 82, 94, 66