In a 15-day survey of air pollution in two European capitals, the mean particulate count (micrograms per cubic meter) in Athens was 39.5 with a standard deviation of 3.75, while in London the mean was 31.5 with a standard deviation of 2.25.
(a) Assuming equal population variances, does this evidence convince you that the mean particulate count is higher in Athens, at α = .05?
(b) Are the variances equal or not, at α = .05?