A-LevelMathematicsProbability and statistics9709/51 · Oct/Nov 2021 · Q24 Marks
A summary of 40 values of x gives the following information: Σ(x − k) = 520, Σ(x − k)² = 9640, where k is a constant.
- (a)Given that the mean of these 40 values of x is 34, find the value of k.[2]
- (b)Find the variance of these 40 values of x.[2]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.
- [M1] Forms an equation involving Σx, Σ(x-k) and k. Accept at a numeric stage with k.
- [A1] Evaluated. [k[=34-13]=21]
- [M1] Values substituted into an appropriate variance formula, accept unsimplified.
- [A1] (72)
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