The mass of a bag of flour produced at a factory is normally distributed with a mean of 1500 g and a standard deviation of 20 g.
Find the probability of a bag weighing more than 1545 g.
The quality control manager suspects that the mean mass of the flour bags has changed.
Write down a null and alternative hypothesis for a two-tailed test.
They take a random sample of 25 bags and find a mean mass of 1512 g.
Test at the 5% significance level whether there is evidence that the mean mass has changed.
390 exam-style questions on OCR A Level Maths 2.4 Statistical Distributions, covering 2.4.1 Discrete probability distributions, 2.4.2 Binomial distribution as a model, 2.4.3 Calculating binomial probabilities, 2.4.4 Mean and variance of the binomial (A-level only), 2.4.5 Normal distribution as a model (A-level only), 2.4.6 Probabilities using the normal distribution (A-level only), 2.4.7 Links to histograms, mean and standard deviation (A-level only), and 2.4.8 Selecting an appropriate distribution (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.