A local authority is considering whether to introduce a policy to get more householders rainwater storage installed. To help with the decision and design of the policy, the current situation needs to be quantified. It has conducted a pilot sampling program with the following results. A random selection of 40 residential properties were surveyed. They found that 13 had rainwater tanks installed with the following total capacities on each property. Residence No Capacity (Thousands of Litres) 1 30 2 3.5 3 40 4 10 5 25 6 40 7 42 68 5 9 10 10 15 11 35 12 13 60 45 a) What are the 95% confidence limits to the estimate of the mean installed capacity of those households with tanks installed? b) How many residences would need to be surveyed to find the mean installed capacity of those households with tanks installed, within plus or minus 10% and with 95% confidence in the result? c) What are the 95% confidence limits of the estimate of the percentage of households with tanks installed? d) Estimate the 95% confidence limits of the estimate of the percentage of households with tanks installed after the number in answer to b above have been surveyed. A Go