7 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.
| Number of incorrect notes | \(1 - 5\) | \(6 - 10\) | \(11 - 20\) | \(21 - 40\) | \(41 - 70\) |
| Frequency | 10 | 5 | 26 | 32 | 18 |
- Draw a histogram to represent this information.
\includegraphics[max width=\textwidth, alt={}, center]{9f0f0e3c-7baf-42eb-a4fb-9ce61922c3cd-10_1488_1493_785_365} - State which class interval contains the lower quartile and which class interval contains the upper quartile.
Hence find the greatest possible value of the interquartile range.
- Calculate an estimate for the mean number of incorrect notes.
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