(a(i))[3]
Determine the value of $\Sigma (x - c)$.
(a(ii))[1]
Given that $c = 50$, determine the mean of these $x$-values.
Mathematics 9709 · AS & A Level · Sampling and estimation
Sampling and estimation — practice question
For $40$ readings of the variable $x$, the information given is that $\Sigma (x - c)^2 = 3099.2$, with $c$ fixed. The standard deviation of those $x$-values is $3.2$.
Worked solution & mark scheme
This 4-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Apply the correct variance formula with substitution: $\sigma^2 = \frac{\sum (x-c)^2}{n} - \left(\frac{\sum (x-c)}{n}\right)^2$” …
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