Mathematics 9709 · AS & A Level · The normal distribution
The normal distribution — practice question
People living in Persham were asked how dependable they thought their internet service was. $12\%$ described it as ‘poor’, $36\%$ described it as ‘satisfactory’ and $52\%$ described it as ‘good’. A random sample of $8$ residents of Persham is chosen.
(a)[3]
Find the probability that more than $2$ but fewer than $8$ of them judge their internet service to be poor or satisfactory.
(b)[5]
Use an approximation to find the probability that more than $72$ of these residents judge their internet service to be good.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “A correct binomial probability set-up, for instance $P(3 \\le X \\le 7)=1-P(0,1,2)$ or a matching equivalent sum.” …