(a)[3]
Find the probability that the mean time taken to complete the test, for a random sample of $40$ students, is less than $123$ minutes.
(b)[1]
Explain whether the Central Limit Theorem had to be used in the solution to part (a).
Mathematics 9709 · AS & A Level · Sampling and estimation
Sampling and estimation — practice question
The completion times, measured in minutes, for students taking a test are distributed as $N(125, 36)$.
Worked solution & mark scheme
This 4-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Use standardisation with $z=\frac{123-125}{6/\sqrt{40}}$ (the $\sqrt{40}$ must be shown).” …
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