12.32 Due to increased energy shortages and costs, utility companies are stressing ways in which home and apartment utility bills can be cut. One utility company reached an agreement with the owner of a new apartment complex to conduct a test of energy-saving plans for apartments. The tests were to be conducted before the apartments were rented. Four apartments were chosen that were identical in size, amount of shade, and direction faced. Four plans were to be tested, one on each apartment. The thermostat was set at 75F in each apartment, and the monthly utility bill was recorded for each of the three summer months. The results are listed in table below.

Treatment 1: no insulation Treatment 2: insulation in walls and ceilings Treatment 3: no insulation; awnings for windows Treatment 4: insulation and awnings for windows a Is there evidence that the mean monthly utility bills differ for the four treatments? Use 0.01.
b Is there evidence that blocking is important, that is, that the mean utility bills differ for the three months? Use 0.05.

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Treatment Month 1 2 3 4 June $74.44 $68.75 $71.34 $65.47 July 89.96 73.47 83.62 72.33 August 82.00 71.23 79.98 70.87