A-LevelMathematicsProbability and statistics9709/62 · Oct/Nov 2021 · Q36 Marks
The probability that a certain spinner lands on red on any spin is p. The spinner is spun 140 times and it lands on red 35 times.
- (a)Find an approximate 96% confidence interval for p.[3]
- (b)From three further experiments, Jack finds a 90% confidence interval, a 95% confidence interval and a 99% confidence interval for p. Find the probability that exactly two of these confidence intervals contain the true value of p.[3]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.
- [M1] Expression of correct form (allow M1 for just one side stated). Must be a z-value.
- [B1] z = 2.054 or 2.055
- [A1] 0.175 to 0.325 (3sf) Must be an interval.
- [M1] 0.90 × 0.95 × 0.01
- [M1] + 0.90 × 0.05 × 0.99
- [M1] + 0.10 × 0.95 × 0.99
- [A1] 0.147
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