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** Index**

In this chapter we discuss the power of the twin study to detect
variance components in behavioral characters. Our discussion is not
in any way intended to be an exhaustive description of the power of
the twin study under all possible combinations of causal factors and
model parameters. Such a description is in large part available for
the continuous case (Martin *et al*.,
1978) and the ordinal case (Neale *et al*., 1994),
and there is an extensive comparison of the power of various
designs to detect cultural transmission (Heath
*et al*., 1985). As we move out of the framework of the
univariate classical twin study to consider multivariate hypotheses
and data from additional classes of relatives, a comprehensive
treatment rapidly becomes unmanageably large. Fortunately, it seems
rather unnecessary because the prospective researcher usually has
certain specific aims of a study in mind, and often has a reasonable
idea about the values of some of the parameters in the model. This
information can be used to prune the prodigious tree of possible
scenarios to manageable proportions. All that is required is an
understanding of the factors contributing to power and the principles
involved, which we aim to provide in (Section 7.2) and
Section 7.3 respectively. We illustrate these methods
with a limited range of examples for continuous (Section 7.4)
and categorical (Section 7.5) twin data.

** Next:** 2 Factors Contributing to
** Up:** 7 Power and Sample
** Previous:** 7 Power and Sample
** Index**
Jeff Lessem
2002-03-21