Table 4.

Required sample size per group for ANCOVA vs. ANOVA assuming α = 0.05

			ANCOVA Power		ANOVA Power
Type of TT Test	Effect of Altitude	Effect of Treatment*	80%	95%	80%	95%
720-kJ cycle	20%	5%	243	402	258	429
		20%	17	27	17	29
	33%	5%	198	328	210	349
		20%	14	22	14	23
11.2-km run	20%	5%	71	120	74	123
		20%	6	8	6	9
	33%	5%	60	98	60	100
		20%	5	7	5	8
3.2-km run	20%	5%	154	254	247	409
		20%	11	18	17	27
	33%	5%	126	208	201	310
		20%	10	15	14	22

ANCOVA, analysis of covariance; TT, time trial.

^*Assumes an attenuation from placebo group, e.g., if there is a 20% increase from altitude alone, then a 5% treatment effect would result in a 1% attenuation in the increase from altitude (20% vs. 19% increase in control vs. treatment groups. respectively).