A random sample of size nnn is taken from a population that is normally distributed with mean 252525 and standard deviation 444. Find the minimum sample size such that the probability of the sample mean being greater than 27.527.527.5 is less than 1%1\%1%.
390 exam-style questions on AQA A Level Maths 2.4 N: Statistical distributions, covering 2.4.1 Discrete distributions and the binomial, 2.4.2 The Normal distribution (A-level only), and 2.4.3 Selecting an appropriate distribution (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.