The time taken by a coach to travel from Belfast to Enniskillen, in minutes, is Normally distributed with mean 220 minutes and standard deviation 8 minutes.
Find the probability that a randomly chosen journey takes longer than 235 minutes. Give your answer to 3 significant figures.
The bus company suspects that the mean journey time has changed. A random sample of 10 journeys is taken, and the mean time for the sample is 230 minutes.
Stating your hypotheses clearly, carry out a two-tailed test at the 1% significance level to investigate the company's suspicion. You may assume that the standard deviation is still 8 minutes.
284 exam-style questions on CCEA A Level Maths 4.5 Statistical distributions (A-level only), covering 4.5.1 Statistical distributions (A-level only) and 4.5.2 Statistical distributions (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.