(i)[2]
Show that the chance that she picks exactly $2$ paperback books is $\frac{3}{14}$.
(ii)[3]
Draw the probability distribution table for $X$.
(iii)[2]
You are told that $\text{E}(X) = 3$. Calculate $\mathrm{Var}(X)$.
Mathematics 9709 · AS & A Level · Sampling and estimation
Sampling and estimation — practice question
Mrs Hunt is given $6$ paperback books and $2$ hardback books by a book club. She randomly selects $4$ of them to take away on holiday. The random variable $X$ stands for the number of paperback books she picks.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct probability statement for exactly 2 successes, e.g. $P(X=2)=\frac{\binom{6}{2}}{\binom{8}{4}}$ or an equivalent method” …
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