Mathematics 9709 · AS & A Level · Continuous random variables

Continuous random variables — practice question

(a)[3]

The random variable $X$ has a normal distribution with mean $82$ and standard deviation $7.4$. Determine the value of $q$ for which $P(82-q < X < 82+q) = 0.44$.

(b)[4]

The random variable $Y$ follows a normal distribution with mean $\mu$ and standard deviation $\sigma$. You are told that $5\mu = 2\sigma^2$ and also that $P\left(Y < \tfrac{1}{2}\mu\right) = 0.281$. Determine the values of $\mu$ and $\sigma$.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: Appropriate application of the standard normal distribution with $P(X<q+82)=0.72$ and $z=0.58$

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