| Characteristics | Number |
| F/t test | p-value |
| Age range (Years) | ||||
| ≤30 | 8 | 6.5 ± 2.1 | ||
| 31 - 40 | 218 | 7.4 ± 2.9 | 0.385 | 0.764 |
| 41 - 50 | 28 | 7.7 ± 3.0 | ||
| ≥51 | 2 | 7.5 ± 3.5 | ||
| Sex | ||||
| Male | 201 | 7.4 ± 3.0 | 0.653 | 0.514 |
| Female | 55 | 7.7 ± 2.4 | ||
| Education | ||||
| Completed primary school | 28 | 7.4 ± 3.0 | ||
| Completed secondary school | 115 | 7.2 ± 2.9 | 0.764 | 0.467 |
| Tertiary education | 113 | 7.7 ± 2.7 | ||
| Years in operation | ||||
| ≤5 | 143 | 7.9 ± 2.7 | 4.270 | 0.006 |
| 6 - 10 | 83 | 6.5 ± 2.8 | ||
| 11 - 15 | 26 | 7.7 ± 3.1 | ||
| ≥16 | 4 | 8.0 ± 2.1 |