STAT 496, Spring 2011 Homework Assignment #4, Due by Thursday, March 3 1. In an experiment on the effectiveness of laundry detergents, 2 brands of detergent and 2 water temperatures are used in a 2 2 factorial experiment. A standard load of laundry consists of 2 pairs of jeans, 5 sets of cotton underwear, 5 pairs of white crew socks, 5 cotton shirts, and 3 cotton towels. Each load is mixed with 100 grams of top soil, shaken to remove loose dirt, and weighed. Five standard laundry loads are washed for each of the combinations. One washing machine is used. The assignment of detergent brand and water temperature to a laundry load and the order of washing are completely randomized. The amount of dirt removed (difference between starting weight and ending weight after the load is washed and dried) is the response. The data are given below. Detergent Brand Water Temperature Amount of Dirt Removed (g) Mean Variance X Warm 13 16 16 14 17 15.2 2.7 Y Warm 17 19 20 17 20 18.6 2.3 X Hot 18 16 17 19
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