In each of 4 years a random sample of 100 voters (different each year) are asked if they support a political party. The numbers each year who support the party are 41, 32, 35, and 33.
(a) Give a 95 percent confidence interval for the percentage who sup- port the party in the first year.
(b) Give a 95 percent confidence interval for the change in the per- centage who support the party between the first and second years.
(c) Can you conclude that support for the party is constant over the 4 years? Explain.