Table 2.

Mean, standard deviation, and difference between chronological age and dental age according to Willems method using Student’s t-test

Age group (years)	Sex	n	Mean±SD			95 % CI of mean difference		t	P
			CA	DA	Difference between CA and DA	Lower	Upper
10	Boy	28	10.03±0.58	9.96±0.84	0.07±0.19	−0.32	0.45	0.350	0.728
	Girl	21	9.79±0.56	10.0±1.08	−0.25±0.27	−0.79	0.29	−0.937	0.354
11	Boy	13	10.85±0.50	10.6±0.88	0.19±0.28	−0.39	0.77	0.688	0.498
	Girl	10	10.85±0.73	10.9±1.52	−0.10±0.53	−1.22	1.01	−0.197	0.846
12	Boy	10	11.85±0.67	12.2±1.78	−0.39±0.60	−1.65	0.87	−0.645	0.527
	Girl	19	11.89±0.74	11.3±0.83	0.61±0.25	0.095	1.13	2.399	0.022
13	Boy	25	13.22±0.41	13.5±1.01	−0.30±0.22	−0.74	0.14	−1.377	0.175
	Girl	20	13.21±0.48	12.9±0.81	0.32±0.21	−0.10	0.75	1.542	0.131
14	Boy	33	13.93±0.57	14.4±1.41	−0.43±0.27	−0.95	0.10	−1.614	0.111
	Girl	26	14.30±0.72	13.8±0.92	0.54±0.23	0.08	1.00	2.362	0.022

P<0.05 is statistically significant. SD: Standard deviation, CI: Confidential interval, CA: Chronological age, DA: Dental age