ABSTRACT

Both longitudinal and multilevel designs can provide invaluable empirical evidence for many, if not most, of the central assertions made by theories in the social and behavioral sciences (Baltes & Nesselroade, 1979; Menard, 1991). However, because such designs often involve considerable investments of time and money, their use is only justifiable if the resulting data can be analyzed adequately and thereby represented clearly. More often than not, however, disillusionment is part of the researchers’ experience after the longitudinal or multilevel data are collected. For example, the puzzling number of different ways to analyze longitudinal data is likely to frustrate many researchers who neither consider themselves experts in statistics nor intend to become one. And multilevel designs also offer a plethora of complexities when it comes to decomposing the various sources of variability in the participants’ responses.