The operating time of a component is normally distributed with known standard deviation 10 hours. A manufacturer claims that the population mean is 120 hours. A lower-tailed test is to use random samples of 25 components at the 2.5% significance level.
Find the critical value for the sample mean.
A sample has mean 116.4 hours. Complete the test in context.
328 exam-style questions on WJEC A Level Maths 4.2 Statistical distributions (A-level only), covering 4.2.1 Statistical distributions (A-level only), 4.2.2 Statistical distributions (A-level only), and 4.2.3 Statistical distributions (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.