3. An experiment is conducted to test whether the installation of cavity-wall insulation reduces the amount of energy consumed in houses. Out of twenty otherwise similar houses on a housing estate,...

Extracted text: 3. An experiment is conducted to test whether the installation of cavity-wall insulation reduces the amount of energy consumed in houses. Out of twenty otherwise similar houses on a housing estate, ten are selected at random for insulation. The total energy consumption over a winter is measured for each house. The data, in are as follows. Without insulation With insulation 12.6, 11.8, 12.8, 11.4, 14.4, 12.3, 11.5, 10.8, 9.9, 9.5, 10.0,10.4, 10.7 11.8, 13.2, 11.0, 11.8 7.5,11.8, 10.1 Use a Mann Whitney U-test to test the null hypothesis that the insulation has no effect against the alternative that it reduces energy consumption. Use the 5% level of significance.