Table 9.

Calculated sample size requirement to detect an improvement in insulin sensitivity based on a baseline serum 25-hydroxyvitamin D concentration of 40 ng/mL (100 nmol/L) and a power of 0.80 and alpha of 0.05

Initial serum 25-hydroxy-vitamin D concentration		Estimated insulin sensitivity index(μM/min/m2/pM)	Improvement in insulin sensitivity index with postintervention Serum 25-hydroxyvitamin D concentration 40 ng/mL (100 nmol/L)	Diabetes reduction based on the Diabetes Prevention Program	Sample size
ng/mL	nmol/L
10	25	4.1326	0.8664	0.4361	340
15	37	5.4144	0.4246	0.2118	1602
20	50	6.2812	0.2280	0.1121	5934
25	62	6.8674	0.1232	0.0589	21878
30	75	7.2638	0.0619	0.0278	99260
35	87	7.5319	0.0241	0.0086	1041162