(a)[2]
Determine the mean for the complete set of 45 values of $x$.
(b)[2]
Determine the standard deviation for the full set of 45 values of $x$.
Mathematics 9709 · AS & A Level · Representation of data
Representation of data — practice question
For 20 values of $x$, the totals are $\sum (x - 30) = 439$ and $\sum (x - 30)^2 = 12\,405$. For a further 25 values of $x$, the totals are $\sum (x - 30) = 470$ and $\sum (x - 30)^2 = 11\,346$.
Worked solution & mark scheme
This 4-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Applying the mean formula to all 45 values: $\frac{439+470}{45}+30$ (or an equivalent algebraic method).” …
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