It’s not often that taxes are popular, but when Environics surveyed 1023 adult British Columbians in 2011, it found 54% in favour of the carbon tax in that province. At $25/tonne of carbon, the tax adds only 5¢ to the price of a litre of gasoline.

a) Calculate a 90% confidence interval for the percentage of British Columbians in favour of the carbon tax in 2011 and interpret the meaning of your interval in words.

b) Phrase your confidence interval in the form commonly used by the media. For example, “x% of Ontarians support the X political party. This result is accurate to plus or minus y%, n times out of N.”

c) How many British Columbian adults would Environics need to survey in order to reduce the width of this confidence interval by 25%?

d) How much wider is the 95% confidence interval than the 90% interval you calculated in (a)? Give your answer as the ratio between the widths of the two confidence intervals.