Table I.

Intra-individual variation in cycle length (min to max) for different numbers of contributory cycles.

Number of days difference (min–max)	Percentage of cycles with each level of variation, by number of completed cycles
	2 (n = 3682)	3 (n = 2152)	4 (n = 1143)	5 (n = 697)	6 (n = 465)
0	11.5	2.3	0.6	0.0	0.0
1	21.7	10.7	7.0	2.7	1.1
2	18.1	14.5	12.5	6.5	6.9
3	12.0	15.7	13.9	13.4	10.7
4	8.6	13.8	13.1	13.4	13.8
5	6.6	9.2	12.0	13.6	15.7
6	5.0	6.5	7.9	10.2	9.6
7	3.9	6.0	6.9	8.0	6.9
8	2.8	4.6	5.5	6.6	7.5
9	2.3	3.3	4.7	4.7	6.3
10	1.8	2.7	3.8	6.0	5.2
11	1.3	2.5	2.1	3.7	4.4
12	1.0	2.1	2.0	2.2	2.7
>12	2.7	5.3	6.9	7.7	8.0