The mass of a high-precision turbine blade is modelled by a normal distribution with a mean of 450.0450.0450.0 g and a standard deviation of 12.412.412.4 g. After a change in the manufacturing process, a quality control engineer suspects that the mean mass of the blades has decreased. A random sample of 505050 blades is measured, and the sample mean mass is found to be 446.2446.2446.2 g. Carry out a hypothesis test at the 2%2\%2% significance level to investigate the engineer's suspicion.
130 exam-style questions on Edexcel A Level Maths 3.7 Hypothesis Testing with the Normal Distribution. Each one has a worked solution and a mark scheme showing where the marks go.