| Interval | Lower Boundary-Upper Limit | F | X | F * X |
| 60 - 63 | 59.5 - 63.5 | 3 | 61 | 185 |
| 64 - 67 | 63.5 - 67.5 | 5 | 65 | 328 |
| 68 - 71 | 67.5 - 71.5 | 6 | 69 | 417 |
| 72 - 75 | 71.5 - 75.5 | 6 | 73 | 441 |
| 76 - 79 | 75.5 - 79.5 | 7 | 77 | 543 |
| 80 - 83 | 79.5 - 83.5 | 1 | 81 | 82 |
| Total | 28 | 426 | 1996 | |
| Average |
|
| 71 | |