A researcher wishes to estimate the proportion of Canadians who are in favour of the Kyoto Protocol's call for the reduction of emissions of greenhouse gases. She wants to be 99% confident that her estimate is within 5% of the true proportion.
a) How large a sample should be taken if in a prior survey of Canadians, 70% were in favour of the Kyoto Protocol?
b) If no estimate of the sample proportion is available, how large should the sample be?