Mathematics 9709 · AS & A Level · Discrete random variables
Discrete random variables — practice question
A fair ordinary die is rolled over and over until either a 1 or a 6 appears.
(a)[3]
Find the probability that obtaining a 1 or a 6 requires at least 3 throws but no more than 5 throws.
(b)[3]
In a separate trial, the die is thrown 3 times. The random variable $X$ counts how many times a 1 or a 6 is obtained. Draw the probability distribution table for $X$.
(c)[2]
Find the value of $\text{E}(X)$.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “At least one suitable term of the form $(1-p)p^k$ with $0 \le p \le 1$.” …