Table 3. Average PTSSC-15 total score (by grade, gender, or period).

Grade group	Gender	Months after disaster
		2011			2012			2013				F	P value
		After 8 months			After 20 months			After 30 months
		M	SD	N	M	SD	N	M	SD	N
Kindergartners	Boys	15.1	12.5	119	13.2	11.6	111	15.8	13	95	Gender ×Period	0.021	N.S.
	Girls	15.7	12.8	127	14.2	12.5	127	16.4	10.7	123	Period	2.415	N.S.
											Gender	0.64	N.S.
1st–3rd grade	Boys	17.4	12.8	1866	16.4	12.9	1632	15.8	12.5	1592	Gender ×Period	0.212	N.S.
	Girls	18.2	12.8	1736	16.8	12.6	1581	16.4	12.7	1615	Period	16.18	<0.0001
											Gender	5.721	<0.05
4th–6th grade	Boys	19.6	14.4	1975	17.9	13.9	1792	18.7	14	1854	Gender ×Period	2.832	N.S.
	Girls	21.7	14.7	1973	18.6	14	1798	19.5	13.9	1807	Period	27.5	<0.0001
											Gender	20.06	<0.0001
7th–9th grade	Boys	21.3	14.7	1979	19.5	14	1767	20	14.2	1893	Gender ×Period	0.555	N.S.
	Girls	26	15.5	1864	23.7	14.8	1789	24.9	15.1	1833	Period	18.11	<0.0001
											Gender	270.9	<0.0001

M, mean; SD, standard deviation; N, number of cases; N.S., not significant.