Mathematics 9709 · AS & A Level · Sampling and estimation
Sampling and estimation — practice question
A random sample made up of 5 observations of a variable $X$ is shown here: $2,\ 3,\ 3,\ 5,\ a$.
(a)[1]
Find an expression, in terms of $a$, for the mean of this set of values.
(b)[3]
It is stated that the unbiased estimate of the population variance of $X$ from these values is $4$. Also, $a$ is positive. Form and simplify a quadratic equation in terms of $a$, then determine the value of $a$.
Worked solution & mark scheme
This 4-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct mean is $\frac{13+a}{5}$” …