The lifetime of a certain type of battery is normally distributed with a mean of 60 hours. Given that 8% of the batteries last less than 48 hours, find the standard deviation of the lifetimes.
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.