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.
Practise Edexcel A Level Maths The Normal Distribution with exam-style questions for A Level Maths. 100 questions covering The Normal Distribution, Finding Probabilities for Normal Distributions, The Inverse Normal Distribution Function, The Standard Normal Distribution, Finding the mean and standard deviation, Approximating a Binomial Distribution, and Hypothesis Testing with the Normal Distribution, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.