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.
316 exam-style questions on OCR A Level Maths 2.5 Statistical Hypothesis Testing, covering 2.5.1 The language of hypothesis testing, 2.5.2 Hypothesis test for a binomial proportion, 2.5.3 Inference and significance level, 2.5.4 Sample mean as a random variable (A-level only), 2.5.5 Hypothesis test for the mean of a normal distribution (A-level only), 2.5.6 Pearson's product-moment correlation coefficient, and 2.5.7 Hypothesis test using Pearson's coefficient (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.