The time taken for a computer script to complete a specific task is normally distributed with a mean of 40 seconds and a standard deviation of 6 seconds.
Find the probability of the script taking longer than 50 seconds.
A developer suspects that a recent update has changed the mean completion time.
Write down a null and alternative hypothesis for a two-tailed test.
A random sample of 9 scripts is run, resulting in a mean completion time of 45 seconds.
Test at the 1% significance level whether there is evidence that the mean completion time has changed.
351 exam-style questions on AQA A Level Maths 2.4.2 The Normal distribution (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.