Factor and simplex models for repeated Measures: Application to two psychomotor measures of alcohol sensitivity in twins

Factor and simplex models for repeated measures: application to two psychomotor measures of alcohol sensitivity in twins.

As part of a larger study, data on arithmetic computation and motor coordination were obtained from 206 twin pairs. The twins were measured once before and three times after ingesting a standard dose of alcohol. Previous analyses ignored the time-series structure of these data. Here we illustrate the application of simplex models for the genetic analysis of covariance structures in a repeated-m...

The genetic analysis of repeated measures. I. Simplex models.

The well-known simplex model is extended to a model that may be used for the genetic and environmental analysis of covariance structures. This "double" simplex structure can be specified as a LISREL model. It is shown that data which give rise to a simplex correlation structure, such as repeated-measures data, do not fit a factor-analysis model. The parameter estimation of the simplex model is ...

Random coefficient repeated measures models

Models of accuracy in repeated-measures designs

Accuracy is often analyzed using analysis of variance techniques in which the data are assumed to be normally distributed. However, accuracy data are discrete rather than continuous, and proportion correct are constrained to the range 0–1. Monte Carlo simulations are presented illustrating how this can lead to distortions in the pattern of means. An alternative is to analyze accuracy using logi...

Repeated Measures

Repeated measures refer to the observations taken on the same subject (plant, animal, person, etc). There is usually a variation among the subjects, which is modeled by random effects. Here is an example. A completely randomized design with a single factor (with fertilizer or without). Each treatment is applied to three plants and the root length of each plant is measured on five occasions (wee...