Table 3.

Noncentrality Parameters and Powers for TDTs Based on Grandparents as Compared with Parents, Together with Asymptotic Relative Efficiencies^[Note]

	χ2 Noncentrality Parameter (Power)b for
	Grandparental-Transmission Testd with		Parental-Transmission Test with
Scenarioa	1 df	2 df	1 dfe	2 df	AREc for Grandparents vs. Parents
1, 1, 1, 1	.0000 (.05)	.0000 (.05)	.0000 (.05)	.0000 (.05)	…
2, 2, 1, 1	.0576 (.92)	.0632 (.90)	.0368 (.77)	.0408 (.73)	1.57
2, 4, 1, 1	.0785 (.98)	.0785 (.95)	.0498 (.88)	.0498 (.81)	1.58
1, 1, 2, 4	.0092 (.27)	.0093 (.21)	.0000 (.05)	.0000 (.05)	∞
1, 1, 3, 9	.0276 (.65)	.0282 (.56)	.0000 (.05)	.0000 (.05)	∞
1, 3, 1, 1	.0037 (.14)	.0177 (.37)	.0025 (.11)	.0127 (.28)	1.48
1, 3, 2, 2	.0289 (.67)	.0479 (.80)	.0051 (.17)	.0216 (.44)	5.67
2, 4, 1.5, 2	.1248 (1.00)	.1248 (1.00)	.0582 (.93)	.0582 (.87)	2.14

Note.— Calculations assumed a stratified population in which half have a baseline risk of .01 and an allele prevalence of .05 and the other half have a baseline risk of .03 and an allele prevalence of .10.

^aThe numbers denoting each scenario represent R₁, R₂, S₁, and S₂, respectively.

^bExample powers (for a level-.05 test) are given in parentheses for studies with 200 families.

^cBased on 1-df LRTs. ARE = asymptotic relative efficiency.

^dTest 2.

^eBased on the log-linear model with parental mating type and C as predictors.