Table 3.

Simulations Investigating the Impact on Power of the Ascertainment of Trios with an Affected Parent and an Affected Offspring^[Note]

	Result for ResidualFamilial Correlation Level
Test andStatus of Ascertainmentof Affected Parents	.0	.1	.6
TDTW:
Without ascertainment	.33	.35	.36
With ascertainment	.49	.49	.17
FAMW:
Without ascertainment	.46	.55	.60
FAMW*:
With ascertainment	.99	.99	.99

Note.— The disease model follows multiplicative model 8 of Whittaker and Lewis (1998, table 2). In all cases, 100 trios are used, and the ascertainment is for either only the offspring being affected or at least one parent being affected in addition to offspring. Note that the FAM_W* test is conditional on ascertaining an affected parent, as described in the text. Correct type I error rates are obtained for all tests under all scenarios when no genetic effect is simulated.