A discrete random variable Y Y\,Y has a distribution that is approximately symmetric and bell-shaped, with mean 90 and variance 72. It is modelled by X∼N(90,72)X\sim N(90,72)X∼N(90,72).
Use a continuity correction to estimate P(80≤Y≤100)P(80\leq Y\leq100)P(80≤Y≤100).
State one reason why the quality of this approximation should be checked using the original distribution.
390 exam-style questions on OCR (MEI) A Level Maths 2.4 Probability Distributions, covering 2.4.1 Recognise binomial situations, 2.4.2 Probability of success p, 2.4.3 Calculate binomial probabilities, 2.4.4 Mean of the binomial distribution, 2.4.5 Expected frequencies for binomial, 2.4.6 Probability functions and discrete random variables, 2.4.7 Numerical probabilities for a simple distribution, 2.4.8 Normal distribution as a model (A-level only), 2.4.9 Shape of the Normal curve (A-level only), 2.4.10 Linear transformation and standardising (A-level only), 2.4.11 Symmetry and inflection of Normal curve (A-level only), 2.4.12 Calculate probabilities from a Normal distribution (A-level only), 2.4.13 Model with probability distributions, and 2.4 Probability Distributions. Each one has a worked solution and a mark scheme showing where the marks go.