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Calculate the standard deviation of the times taken.
Mathematics 9709 · AS & A Level · Continuous random variables
Continuous random variables — practice question
Over 250 working days, the time taken, $t$ hours, to deliver letters along a particular route is recorded each day. The average time is $2.8$ hours. If $\sum (t - 2.5)^2 = 96.1$, determine the standard deviation of the times taken.
Worked solution & mark scheme
This 3-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Coded mean $=0.3$ used and substitution into the variance formula, e.g. $\sum (t-2.5)=75$ with divisor $250$” …
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