A-LevelMathematicsProbability and statistics9709/53 · Oct/Nov 2021 · Q26 Marks

Lakeview and Riverside are two schools. The pupils at both schools took part in a competition to see how far they could throw a ball. The distances thrown, to the nearest metre, by 11 pupils from each school are shown in the following table. Lakeview 10 14 19 22 26 27 28 30 32 33 41 Riverside 23 36 21 18 37 25 18 20 24 30 25

(a)Draw a back-to-back stem-and-leaf diagram to represent this information, with Lakeview on the left-hand side.[4]
(b)Find the interquartile range of the distances thrown by the 11 pupils at Lakeview school.[2]

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 2021). The mark or mark type is shown in brackets.

[B1] Correct stem, ignore extra values.
[B1] Correct Lakeview labelled on left, leaves in order from right to left and lined up vertically, no commas.
[B1] Correct Riverside labelled on same diagram, leaves in order and lined up vertically, no commas.
[B1] Correct key for their diagram, need both teams identified and 'm' stated at least once here or in leaf headings or title.
[SC] If 2 separate diagrams drawn: SC B1 if both keys meet these criteria.
[M1] (30 < UQ < 33) – (14 < LQ < 22)
[A1] WWW

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