(a) Briefly explain the difference between a one-tailed test and a two-tailed test.
(b) State, with a reason, which type of test would be more appropriate to test the claim that this decade's average temperature is greater than the last decade's.
(a) Give one advantage and one disadvantage of
a sample survey,
a census.
(b) Suggest a situation in which each could be used.
A pharmaceutical company produces an ointment for earache that, in \(80 \%\) of cases, relieves pain within 6 hours. A new drug is tried out on a sample of 25 people with earache, and 24 of them get better within 6 hours.
(a) Test, at the \(5 \%\) significance level, the claim that the new treatment is better than the old one. State your hypotheses carefully.
A rival company suggests that the sample does not give a conclusive result;
(b) Might they be right, and how could a more conclusive statement be achieved?