The following back-to-back stem-and-leaf diagram represents the monthly salaries, in dollars, of 27 employees at each of two companies, A and B. Company A 5 4 1 1 0 25 4 4 5 6 6 7 9 9 8 7 2 1 0 26 0 1 3 5 5 7 9 9 8 6 4 2 1 0 27 1 3 4 6 6 8 8 6 5 4 2 0 28 0 1 2 2 2 9 8 5 29 1 30 9 Key: 1|27| 6 means $2710 for company A and $2760 for company B

Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

1. [B1] Median = 2710. Must be identified, condone Q2. Ignore units throughout.
2. [M1] 2840-2610. 2820 < UQ < 2850 – 2600 < LQ < 2620.
3. [A1] 230. www. If M0 scored SC B1 for 230 www. If key ignored consistently: B0 Median = 271 SC M1 282 < UQ < 285 – 260 < LQ < 262 SC A1 23.
4. [B1] All 5 key values for B plotted accurately in standard format using a linear scale with 3 identified values. Labelled B. Scale at least 1 cm = $100.
5. [B1FT] All 5 key values for A, FT from (a), plotted accurately in standard format using a linear scale with 3 identified values. Labelled A. Scale at least 1cm = $100
6. [B1] Whiskers not through box for both, not drawn at corners of boxes, single linear scale for the diagram and labelled 'salaries' (oe) and $.
7. [B1] Examples: Mean less appropriate than median because of extreme value for company B [at $3090]. No, extreme value in company B. No, $3090 is an anomaly. Must refer to company B, may be implied by appropriate use of $3090. Must include an indication that the mean is not appropriate. No contradictory statements can be present, e.g. acceptable comment with 'but mean could be used for company A'. Condone reference to $309.