The battery life, in hours, for a fully charged wireless keyboard is normally distributed with mean 60 hours and standard deviation 8 hours. Hannah has a fully charged wireless keyboard. Give your answers to 3 significant figures.
Find the probability that the keyboard lasts longer than 55 hours.
Hannah uses her keyboard for 55 hours. Find the probability that Hannah's keyboard lasts for another 10 hours.
Hannah believes that the mean battery life of the wireless keyboards are longer than 60 hours. She took a random sample of 16 of these keyboards and found that their mean lifetime was 63.5 hours. Stating your hypotheses clearly and using a 5% level of significance, test Hannah's belief.
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.