Number of participants included in a study of irritable bowel syndrome and chronic fatigue 3 years after acute giardiasis
| Exposed, No (%) | Controls, No (%) | |||
| Total | Group 1 | Group 2 | ||
| Questionnaires mailed | 1252 (100.0) | 3598 (100.0) | 2504 (100.0) | 1094 (100.0) |
| Questionnaires received | 1225 (97.8) | 3555 (98.8) | 2475 (98.8) | 1080 (98.7) |
| Questionnaires returned | 817 (65.3) | 1133 (31.5) | 862 (34.4) | 271 (24.8) |
| Questionnaires accepted | 817 (65.3) | 1128 (31.4) | 859 (34.3) | 269 (24.6) |