2 A small chapel was open to visitors for 55 days during the summer of 2015. The table summarises the daily numbers of visitors.
| Number of visitors | Number of days |
| 20 or fewer | 1 |
| 21 | 2 |
| 22 | 3 |
| 23 | 6 |
| 24 | 8 |
| 25 | 10 |
| 26 | 13 |
| 27 | 7 |
| 28 | 2 |
| 29 | 1 |
| 30 or more | 2 |
| Total | 55 |
- For these data:
- state the modal value;
- find values for the median and the interquartile range.
- Name one measure of average and one measure of spread that cannot be calculated exactly from the data in the table.
[0pt]
[2 marks] - Reference to the raw data revealed that the 3 unknown exact values in the table were 13,37 and 58.
Making use of this additional information, together with the data in the table, calculate the value of each of the two measures that you named in part (b).
[0pt]
[3 marks]