1. A study compared the effects of four 1-month point-of-purchase promotions on sales. The unit sales for five stores using all four promotions in different months follow.

Free Sample 78 87 81 89 85

On-pack gift 94 91 87 90 88

Cents off 73 78 69 83 76

Refund by mail 79 83 78 69 81

At the 0.01 level of significance, do the promotions produce different effects on sales? [Note: There are 4groups to compare, i.e., the 4 marketing methods.] ** Can you please explain how you get F-critical at the end.**