A-LevelMathematicsProbability and statistics9709/62 · Feb/Mar 2023 · Q14 Marks
Anita carried out a survey of 140 randomly selected students at her college. She found that 49 of these students watched a TV programme called Bunch.
- (a)Calculate an approximate 98% confidence interval for the proportion, p, of students at Anita's college who watch Bunch.[3]
- (b)Carlos says that the confidence interval found in (a) is not useful because it is too wide. Without calculation, explain briefly how Carlos can use the results of Anita's survey to find a narrower confidence interval for p.[1]
Mark scheme
Marking points from the official mark scheme (Feb/Mar 2023). The mark or mark type is shown in brackets.
- [B1] [=0.35]
- [M1] Use of formula of correct form, ft their 49/140, any z (not a probability).
- [B1] Accept 2.326 to 2.329 .
- [A1] Must be an interval.
- [B1] Find a smaller percentage confidence interval/ lower level of confidence
- [B1] ISW if 2 reasons given. Just saying 'use smaller z' oe B0. Accept a correct example e.g. 90% (even if not qualified with statement).
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