NECO 2023 · Paper 1 · Q45
The table shows the scores of students in a Mathematics examination. Find the lower class boundary of the class containing the sixth decile.
| Scores | 41–50 | 51–60 | 61–70 | 71–80 | 81–90 | 91–100 |
|---|---|---|---|---|---|---|
| Frequency | 8 | 12 | 14 | 16 | 8 | 2 |
Worked solution (try it first)
- Add the frequencies: .
- The sixth decile is at , the 36th score.
- The cumulative frequencies are 8, 20, 34, 50, … The first 34 scores fill the classes up to 61–70, so the 36th is in 71–80.
- The lower class boundary of 71–80 is halfway between 70 and 71: 70.5, option D.