The length of the bus journey from Leeds to London is normally distributed with a mean of 220 minutes and a standard deviation of 8 minutes.
Find the probability of a bus taking longer than 235 minutes.
The bus company suspect that the mean bus time has changed.
Write down a null and alternative hypothesis for a two-tailed test.
They take a sample of 10 bus journeys and find a mean time of 230 minutes.
Test at the 1% significance level whether there is evidence that the mean time has changed.
