Question: In a selection of 80 properties on the market the mean age was 42.4 years with a SD of 12.5 years. Give

a) 95% (2 marks)

b) 99% (2 marks)

Confidence limits for the mean age of all properties in the area from which these were selected.

c) How large a sample would be necessary to establish the 95% confidence limits to +/- 1 year? (2 marks)