A call centre claims that the amount of time a worker spends on each phone call can be modelled by a normal distribution with a mean of 8 minutes and a standard deviation of 2 minutes.
Using this model, find the probability that the time the worker spends on a randomly selected phone call is more than 11 minutes.
The call centre manager thinks that the mean time for each phone call is more than 8 minutes. The manager takes a random sample of 20 phone calls and finds that the average time is 8.8 minutes. Test the manager's belief at the 5% significance level. You should state your hypotheses clearly.
355 exam-style questions on OCR (MEI) A Level Maths 2.5 Statistical Hypothesis Testing, covering 2.5.1 Process and language of hypothesis testing, 2.5.2 When to apply 1-tail and 2-tail tests, 2.5.3 Significance level and incorrect rejection, 2.5.4 Null and alternative hypotheses (binomial), 2.5.5 Conduct a binomial hypothesis test, 2.5.6 Critical and acceptance regions (binomial), 2.5.7 Distribution of the sample mean (A-level only), 2.5.8 Hypothesis test for a single mean (A-level only), 2.5.9 Critical and acceptance regions (mean) (A-level only), 2.5.10 Correlation as closeness to a straight line (A-level only), 2.5.11 Inference using a correlation coefficient (A-level only), and 2.5 Statistical Hypothesis Testing. Each one has a worked solution and a mark scheme showing where the marks go.