Table A2.

Difference in gender between included and excluded respondents by grades.

Grade	Included		Excluded		Group Difference
	Male	Female	Male	Female
	n	n	n	n	Chi-Squared 1	p
5	24	21	40	28	χ2 (1, n = 113) = 0.15	0.70
6	45	33	41	30	χ2 (1, n = 149) = 0.0	1.0
7	77	77	33	25	χ2 (1, n = 212) = 0.55	0.46
8	79	64	30	22	χ2 (1, n = 195) = 0.02	0.89
9	87	83	28	18	χ2 (1, n = 216) = 1.01	0.32
10	111	86	24	24	χ2 (1, n = 245) = 0.40	0.53
11	72	81	13	17	χ2 (1, n = 183) = 0.03	0.86
12	25	16	11	4	χ2 (1, n = 56) = 0.29	0.59

¹ Pearson’s chi square test, 2-sided.