7.10. For a random sample of Canadians, 60% indicate approval ofthe prime minister's performance.

A similar poll a month later has a favorable rating of 57%. A 99% confidence interval for the change in the population proportions is (— 0.07,0.01).

Explain why

(a) there may have been no change in support,

(b) if a decrease in support occurred, it may have been fairly important,

(c) if an increase in support occurred, it was probably so small as to be substantively unimportant.