Multifactorial Analysis of Family Data Ascertained Through
Truncation: a Comparative Evaluation of Two Methods of
Statistical Inference
Rao DC; Wette R; Ewens WJ
Division of Biostatistics, Washington University School of Medicine, St.
Louis, MO 63110.
American Journal of Human Genetics,
42(3):506-515 (Mar 1988)
Abstract
When family data are ascertained through single selection based on
truncation, a prevailing method of analysis is to condition the likelihood
function on the proband's actual phenotypic value. An alternative method
conditions the likelihood function on the event that the proband's
measurement lies in the truncation region. Both methods are contrasted
here by using Monte Carlo simulations; identical sets of data were analyzed
using both methods. The results suggest that, under either method, (1)
parameter estimates are nearly unbiased and (2) likelihood-ratio tests of null
hypotheses are approximately distributed as chi 2. However, conditioning on
the proband's actual phenotypic value yields considerably less efficient
estimates and reduced power for hypothesis tests. A corresponding result
also holds under complete ascertainment. It is argued, therefore, that
whenever sufficient information is available on the nature of truncation, the
alternative approach should be used.
Variance component linkage analysis