For a random sample of university teachers, 50%

were positive about the vice chancellor’s performance. A similar poll two months later indicated an approval rate of 47%. A 99% confidence interval for the change in the population proportions is (−0.09, 0.03). Explain why

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

(b) if a decrease in support occurred, it may have been fairly important, whereas if an increase in support occurred, it was probably so small as to be substantively unimportant.