A large-scale ecological study on urban honeybee colonies indicates that 40% of hives survive a particularly harsh winter without human intervention. A researcher monitors a random sample of 20 hives in a specific district.
Find the probability that exactly 7 of these hives survive.
Find the probability that at least 4 of these hives survive.
In a regional survey involving a larger sample of 150 hives, use a suitable approximation to determine the probability that the number of surviving hives is between 52 and 70 inclusive.
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.