Table 3 Chi square test for comparing equal proportions of myopia for the different risk factors
From: Myopia in Bulgarian school children: prevalence, risk factors, and health care coverage
Grouping characteristic | Chi^2 test statistic | Degrees of freedom | P-value |
|---|---|---|---|
School | 51.237 | 3 | < 0.0001 |
Age group (above and below 10) | 7.689 | 1 | 0.0056 |
Gender | 9.597 | 1 | 0.0019 |
Sport (every day versus not every day) | 11.847 | 1 | 0.0006 (43 missing observations) |
Time in front of the screen (less than 4 h versus more or equal to 4 h) | 1.4638 | 1 | 0.2263 (59 missing observations) |
Previous examinations | 48.134 | 1 | < 0.0001 (12 missing observations) |
Parents wear glasses (at least one of the parents to wear glasses versus none of them) | 20.928 | 1 | < 0.0001 (76 missing observations) |