The lengths of steel rods, XXX cm, have a normal distribution with unknown mean μ\muμ cm and known standard deviation σ\sigmaσ cm. A random sample of 64 rods yielded a 95% confidence interval for μ\muμ of (12.18,12.62)(12.18, 12.62)(12.18,12.62).
Without carrying out any further calculations, use this confidence interval to test whether or not μ=12.7\mu = 12.7μ=12.7. State your hypotheses clearly and write down the significance level you have used.
A second random sample, of 80 rods, had a mean length of 12.4512.4512.45 cm.
Calculate a 99% confidence interval for μ\muμ based on this second sample.
209 exam-style questions on CCEA A Level Maths 4.6 Statistical hypothesis testing (A-level only), covering 4.6.1 Statistical hypothesis testing (A-level only), 4.6.2 Statistical hypothesis testing (A-level only), 4.6.3 Statistical hypothesis testing (A-level only), 4.6.4 Statistical hypothesis testing (A-level only), and 4.6.5 Statistical hypothesis testing (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.