Table 1.

Shows the demographic information of participants, including sex, grade, and household, and so on.

Characteristics		n	Percentage (%)
Sex	Boys	273	51.51
	Girls	257	48.49
Grade	2	91	16.70
	3	97	17.80
	4	89	16.33
	5	116	21.28
	6	152	27.89
Family income	<¥50,000	108	27.91
	> = ¥50,000	279	72.09
Age of father	<30	11	2.59
	30–40	304	71.70
	> = 40	109	25.71
Age of mother	<30	30	7.04
	30–40	333	78.17
	> = 40	63	14.79
Education level of father	Junior high school diploma or below	194	45.65
	High school diploma	159	37.41
	Undergraduate degree	72	16.94
Education level of mother	Junior high school diploma or below	221	51.76
	High school diploma	155	36.30
	Undergraduate degree	51	11.94