The lifetime of a certain type of battery is normally distributed with a mean of 48 hours and a standard deviation of 4.5 hours.
Find the probability of a battery lasting longer than 55 hours.
Write down a null and alternative hypothesis for a two-tailed test.
A technician takes a sample of 20 batteries and finds a mean lifetime of 51 hours. Test at the 2% significance level whether there is evidence that the mean lifetime has changed.
616 exam-style questions on Edexcel A Level Maths The Normal Distribution, covering 3.1 The Normal Distribution, 3.2 Finding Probabilities for Normal Distributions, 3.3 The Inverse Normal Distribution Function, 3.4 The Standard Normal Distribution, 3.5 Finding the mean and standard deviation, 3.6 Approximating a Binomial Distribution, and 3.7 Hypothesis Testing with the Normal Distribution. Each one has a worked solution and a mark scheme showing where the marks go.