A factory manufactures steel rods with length L L\,L cm, where L∼N(μ,σ2)L \sim \mathrm{N}(\mu, \sigma^2)L∼N(μ,σ2). From a random sample of rods, an 80% confidence interval for μ \mu\,μ is calculated as (74.36,75.64)(74.36, 75.64)(74.36,75.64).
Find a 95% confidence interval for μ\muμ.
Using the formula for the volume of a rod V=10LV = 10LV=10L, find a 95% confidence interval for the mean volume of these rods.
If four independent random samples are taken and a 95% confidence interval for μ \mu\,μ is calculated for each, find the probability that at least three of these intervals will contain the true value of μ\muμ.
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.