Sampling schemes and the selection of log-linear models for longitudinal data

Because the selection of a sampling scheme can have strong effects on the a dmissibility of log-linear models, the authors discuss these effects for th e multinomial and the product multinomial sampling schemes for prospective and retrospective sampling. In multinomial sampling, marginal frequencies a re not fixed a priori. In product multinomial sampling, uni- or multidimens ional marginal frequencies are considered fixed. Therefore, models must fit these marginal frequencies exactly. A data example illustrates model selec tion using data from a project of family development.