Mathematics 9709 · AS & A Level · Sampling and estimation

Sampling and estimation — practice question

The random variable $T$ represents Tania’s 100 m race times, measured in seconds. It follows a normal distribution with mean $\mu$ and variance $\sigma^2$. A random sample of $40$ of Tania’s races produced the following values: $n = 40$, $\sum t = 560$, $\sum t^2 = 7850$.
(a)[3]

Calculate unbiased estimates for $\mu$ and $\sigma^2$.

(b)[5]

Using your answers to part (a), determine the probability that, in one randomly selected 100 m race, Suki’s time is at least $0.1\text{ s}$ longer than Tania’s time.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: Estimate the mean as $\mu=14$ (accept $\frac{560}{40}$)

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