Table 1. Power calculation for a combination of parameters.

Power	PEPT cases	Total sample size	Allocation ratio	Clinically relevant difference in orthodontic need	Multiple correlation between the exposure and the other independent variables	Alpha
85%	500	1000	1	10%	0.1	0.05
81%	500	1000	1	10%	0.2	0.05
91%	500	1000	1	11%	0.1	0.05
88%	500	1000	1	11%	0.2	0.05
95%	500	1000	1	12%	0.1	0.05
93%	500	1000	1	12%	0.2	0.05
91%	600	1200	1	10%	0.1	0.05
87%	600	1200	1	10%	0.2	0.05
95%	600	1200	1	11%	0.1	0.05
93%	600	1200	1	11%	0.2	0.05
91%	500	1250	1.5	10%	0.1	0.05
87%	500	1250	1.5	10%	0.2	0.05
95%	500	1250	1.5	11%	0.1	0.05
93%	500	1250	1.5	11%	0.2	0.05
93%	500	1500	2	10%	0.1	0.05
90%	500	1500	2	10%	0.2	0.05