A-LevelMathematicsProbability and statistics9709/62 · Oct/Nov 2018 · Q26 Marks
The following back-to-back stem-and-leaf diagram shows the reaction times in seconds in an experiment involving two groups of people, A and B. A B (4) 4200 | 20 | 567 (3) (5) 98500 | 21 | 122377 (6) (8) 98753222 | 22 | 1356689 (7) (6) 876521 | 23 | 45788999 (8) (3) 863 | 24 | 2456788 (7) (1) 0 | 25 | 0278 (4) Key: 5 | 22 | 6 means a reaction time of 0.225 seconds for A and 0.226 seconds for B The median value for group B is 0.235 seconds, the lower quartile is 0.217 seconds and the upper quartile is 0.245 seconds.
- (i)Find the median and the interquartile range for group A.[3]
- (ii)Draw box-and-whisker plots for groups A and B on the grid.[3]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.
- [B1] Correct median (Q2)
- [M1] 0.232 < UQ (Q3) < 0.238 – 0.204 < LQ < 0.219
- [A1] www
- [B1] Linear scale between 0.20 to 0.26 (condone omission of 0.26) axis labelled (time and seconds), at least one box plot attempted, no lines through boxes, whiskers not at corner of boxes
- [B1ft] Labelled correct graph for A, (ft their median/quartiles), condone lines through boxes, whiskers at corner of boxes
- [B1] Labelled correct graph for B, condone lines through boxes, whiskers at corner of boxes
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