A-LevelMathematicsProbability and statistics9709/62 · Feb/Mar 2019 · Q57 Marks

The weights, in kg, of the 11 members of the Dolphins swimming team and the 11 members of the Sharks swimming team are shown below. Dolphins 62 75 69 82 63 80 65 65 73 82 72 Sharks 68 84 59 70 71 64 77 80 66 74 72

(i)Draw a back-to-back stem-and-leaf diagram to represent this information, with Dolphins on the left-hand side of the diagram and Sharks on the right-hand side.[4]
(ii)Find the median and interquartile range for the Dolphins.[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 (Feb/Mar 2019). The mark or mark type is shown in brackets.

[B1] Correct stem can be upside down, ignore extra values,
[B1] Correct Dolphin must be on LHS,
[B1] Correct Sharks on either LHS or RHS of back-to-back. Alignment = half a space, no late entries squeezed in, no crossing out if shape is changed. Condone a separate RHS stem-and-leaf diagram
[B1FT] Correct single key for their single diagram, need both teams identified and 'kg' stated at least once here or in leaf headings or title.
[B1] 72 < UQ < 82 - 62 < LQ < 72
[M1] nfww
[A1] SCB1 if M0 scored for LQ = 65 and UQ = 80

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