taken. If 150 need special election facilities, calculate a 90% confidence interval for the population proportion. What is the upper limit of the confidence interval?
Question 8The national electricity supplier claims that switching off the hot water cylinder at night does not result in saving of electricity. In order to test this claim a newspaper reporter obtains the co-operation of 20 house owners with similar houses and salaries. Ten of the selected owners switch their cylinders off at night. The consumption of electricity in each house over a period of 30 days is measured; the units are kWh (kilowatt-hours). For households that switched off their hot water cylinders (group 1), average consumption over the 30 days was 690kWh with a variance of 460kWh2. For those that did not switch off their hot water cylinders, average electricity consumption was 720kWh with a variance of 360kWh2. Test at 10% significance level the assumption that the average consumption is lower if the cylinder is switched off. What is your decision?