A particular piece of music was played by 91 pianists and for each pianist, the number of incorrect notes was recorded. The results are summarised in the table. [Table: Number of incorrect notes | Frequency] [Table: 1–5 | 10] [Table: 6–10 | 5] [Table: 11–20 | 26] [Table: 21–40 | 32] [Table: 41–70 | 18]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

1. [M1] At least 3 class widths correct and used in a calculation
2. [M1] At least 3 correct frequency densities unsimplified – FT their class widths
3. [A1] All correct heights on a histogram using a linear vertical scale from zero – no FT
4. [B1] Correct upper bar ends (5.5, 10.5, 20.5, 40.5, 70.5) and 4 correct lower bar ends of 5.5, 10.5, 20.5, 40.5. Condone 0 or 1.
5. [B1] Linear scales with at least 3 values indicated on each axis, vertical scale from 0, axes labelled 'fd' and 'no. of (incorrect) notes', or better.
6. [B1] Both UQ and LQ correct
7. [B1 FT] Subtract lower end of their LQ interval from upper end of their UQ interval
8. [M1] At least 4 midpoints correct and used
9. [M1] Correct formula with their midpoints (not upper boundary, lower boundary, class width, frequency density, frequency or cumulative frequency)
10. [A1] Accept 26 or 27