(i)[2]
Find the values of $\Sigma (t - 120)$ together with $\Sigma (t - 120)^2$.
(ii)[2]
Using the values obtained in part (i), calculate the variance of $t$.
Mathematics 9709 · AS & A Level · Sampling and estimation
Sampling and estimation — practice question
The times, $t$ seconds, needed to swim $100\,\text{m}$ were recorded for a set of $9$ swimmers, and the results were: $95,\ 126,\ 117,\ 135,\ 120,\ 125,\ 114,\ 119,\ 136$.
Worked solution & mark scheme
This 4-mark question has a full step-by-step worked solution and mark scheme. One marking point: “An attempt is made to add both $\sum (t-120)$ and $\sum (t-120)^2$.” …
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