For $20$ observations of $x$, the mean is $60$ and the standard deviation is $4$.
(a(i))[3]
Determine the values of $\Sigma x$ and $\Sigma x^2$.
(i)[3]
Determine the values of $\Sigma x$ and $\Sigma x^2$.
(ii)[4]
A further 10 values of $x$ have a total of 550 and a total of squares of 40\,500. Calculate the mean and standard deviation of all 30 values of $x$.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Write $\sum x = 60 \times 20 = 1200$.” …
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