Students in a business statistics course performed a completely randomized design to test the strength of four brands of trash bags. One-pound weights were placed into a bag, one at a time, until the bag broke. A total of 40 bags, 10 for each brand, were used. The data in give the weight (in pounds) required to break the trash bags.
a. At the 0.05 level of significance, is there evidence of a difference in the mean strength of the four brands of trash bags?
b. If appropriate, determine which brands differ in mean strength.
c. At the 0.05 level of significance, is there evidence of a difference in the variation in strength among the four brands of trash bags?
d. Which brand(s) should you buy, and which brand(s) should you avoid? Explain.