Table 1 Comparison of non-participants to participants
| Variables | Categories | Non-participants | Participants | Significance of difference |
|---|---|---|---|---|
| N | 73 | 450 | ||
| Mean age in years (std) | 21.1 (3.6) | 20.6 (2.4) | ns | |
| Years in higher education (std) | 2.3 (1.3) | 3.0 (1.5) | 0.001 | |
| N (%) | N (%) | |||
| Higher Education Institution | A | 15 (20.5) | 114 (25.3) | ns |
| B | 29 (39.7) | 180 (40.0) | ns | |
| C | 29 (39.7) | 156 (34.7) | ns | |
| Ireland is not usual country of residence | 4 (5.5) | 28 (6.2) | ns | |
| Current user of oral contraceptive pill | 39 (55.6) | 269 (59.8) | ns |