Mathematics 9709 · AS & A Level · Sampling and estimation

Sampling and estimation — practice question

Tien recorded the arm lengths, $x$ cm, for $20$ classmates. He obtained $\Sigma x = 1218$ and found that the standard deviation of $x$ was $4.2$.
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Calculate the values of $\Sigma (x - 45)$ and $\Sigma (x - 45)^2$.

Worked solution & mark scheme

This 3-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correctly working out $\sum (x-45)=1218-20\times45=318$” …

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