Table 2

Estimated statistical powers required for two period cross over trials using different sample sizes and durations of follow up for different treatment effects using the number of new enhancing lesions (A.III) and the number of active scans (A.II) as the end point measure

Sample size		Effect (%)		Response variable		Duration of each treatment period (months)
Sample size		Effect (%)		Response variable		2	3	6	9
2×10	30	A.II	3	7	16	19
		A.III	22	35	62	76
	40	A.II	3	7	16	21
		A.III	37	55	83	91
	50	A.II	10	19	40	49
		A.III	56	73	93	98
2×20	30	A.II	27	36	43	52
		A.III	51	69	91	98
	40	A.II	31	39	47	55
		A.III	77	91	92	100
	50	A.II	54	70	82	89
		A.III	92	98	100	100
2×30	30	A.II	49	50	58	70
		A.III	69	87	98	100
	40	A.II	50	52	63	73
		A.III	92	98	100	100
	50	A.II	79	83	93	98
		A.III	99	100	100	100
2×40	30	A.II	52	57	68	79
		A.III	81	95	100	100
	40	A.II	57	60	73	85
		A.III	97	100	100	100
	50	A.II	85	91	98	100
		A.III	100	100	100	100