Choosing a distribution and approximationsEdexcel A-Level Maths: Mind map

Exam questions on Choosing a distribution and approximations

1. Each seed in a very large batch germinates independently with probability 0.45. A random sample of 60 seeds is planted and $X$ is the number that germinate.
   Use a Normal approximation to estimate $P(X\ge30)$.2 marks
2. A school has many students, of whom 10% walk to school. A researcher selects the 25 students in one tutor group and records $X$, the number who walk to school. Students in the same tutor group often live in the same roads.
   Suggest how the researcher could choose the sample so that a binomial model would be more suitable.2 marks
3. A biased coin has probability 0.55 of landing heads. It is tossed 80 times and $H$ is the number of heads.
   Explain why $H$ can be modelled by a Normal distribution, and state the distribution that should be used.3 marks