(a)[2]
Calculate the mean speed for these $70$ cars.
(b)[2]
Sachim, his friend, used $(x - 50)$ values to work out the mean. Find $\sum (x - 50)$.
(c)[2]
The standard deviation for the speeds is $10.6$ km per hour. Calculate $\sum (x - 50)^2$.
Mathematics 9709 · AS & A Level · Sampling and estimation
Sampling and estimation — practice question
Delip recorded the speeds, $x$ km per hour, of $70$ cars on a road with a speed limit of $60$ km per hour. His results are summarised by $\sum (x - 60) = 245$.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Applying the coded mean formula gives $\bar{x}=60+\frac{245}{70}$” …
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