| Class interval | Class midpoint | Class frequency | Relative frequency | Cumulative frequency | |
| Number | Relative | ||||
| 51 - 52 | 51.5 | 3 | 3% | ||
| 53 - 54 | 53.5 | 7 | 8% | 10 | 12% |
| 55 - 56 | 55.5 | 4 | 5% | 14 | 16% |
| 57 - 58 | 57.5 | 7 | 8% | 21 | 24% |
| 59 - 60 | 59.5 | 10 | 12% | 31 | 36% |
| 61 - 62 | 61.5 | 16 | 19% | 47 | 55% |
| 63 - 64 | 63.5 | 9 | 10% | 56 | 65% |
| 65 - 66 | 65.5 | 11 | 13% | 67 | 78% |
| 67 - 68 | 67.5 | 8 | 9% | 75 | 87% |
| 69 - 70 | 69.5 | 4 | 5% | 79 | 92% |
| 71 - 72 | 71.5 | 7 | 8% | 86 | 100% |