The time taken, in minutes, to walk to school was recorded for 200 pupils at a certain school. These times are summarised in the following table. Time taken (t minutes) | t ≤ 15 | t < 25 | t ≤ 30 | t ≤ 40 | t ≤ 50 | t ≤ 70 --------------|--------|--------|--------|--------|--------|-------- Cumulative frequency | 18 | 46 | 88 | 140 | 176 | 200

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.

1. [M1] At least 4 points plotted within tolerance at upper bounds. Linear cf scale 0 < cf < 200 and linear time scale 0 ≤ t ≤ 70, with at least 3 values identified on each. Minimum scale uses at least ½ the grid.
2. [A1] All points plotted correctly. Curve drawn and joined to (0, 0). Axes labelled cumulative frequency (cf), time (t) and minutes (min) – or a suitable title.
3. [B1] Must be identified. Evidence of use of graph must be seen. Strict FT ± ½ square on time axis.
4. [M1] 41 < UQ ≤ 43 - 25 < LQ < 27. If outside of range FT ± ½ square on time axis.
5. [A1] FT
6. [B1] At least 5 correct midpoints or 5 correct frequencies seen.
7. [M1] Correct mean formula using their 6 midpoints (must be within class, not upper bound, not lower bound) condone 1 error and their 6 frequencies (not cumulative frequencies).
8. [A1] Accept 33.7, not 673/20.