Table 1.

Comparison of Age and Menstrual Characteristics Between Vitamin E and Acupressure Groups

			Group		Test statistics
Variable	Duration	SD, IQR, or %	Vitamin E	Acupressure	& P-value
Age (yrs)		Mean (SD)	21.8 (0.8)	20.7 (1.1)	U = 227.00,
		Median (IQR)	22.0 (1.0)	21.0 (1.0	P < 0.001 †
Length of bleeding within each menstrual period (d)		Mean (SD)	6.9 (1.1)	6.6 (0.9)	U = 495.00
		Median (IQR)	7.0 (0.0)	7.0 (1.0)	P = 0.13*
Onset of PD after menarche (yrs)	< 1	n (%)	14.0 (40.0)	12.0 (34.3	${\chi }^2\left(3\right)=$ 0.9
	1–2	n (%)	8.0 (22.9)	10.0 (28.6)	P = 0.80†
	2–3	n (%)	6.0 (17.1)	8.0 (22.9)
	> 3	n (%)	7.0 (20.0)	5.0 (14.3
Length of pain in each menstrual period (hrs)	$\le$24	n (%)	23.0 (65.7)	19.0 (54.3	${\chi }^2\left(3\right)=$ 1.66,
	25–48	n (%)	5.0 (14.3)	12.0 (34.3)	P = 0.13†
	49–72	n (%)	7.0 (20.0)	4.0 (11.4

^* Mann–Whitney-U test; ^†${\chi }^2$ test.

Bolding denotes statistical significance.

yrs, years; d, day; hrs, hours; PD, primary dysmenorrhea; SD, standard deviation; IQR, interquartile range; U, probability distribution.