Mixed Models

In many experimental design situations, one or more of the factors in the study may be random factors. Thatis, the levels of those factors are actually a sample from a larger population of levels and inferences are desiredabout the population of factor levels (e.g., the variance of the population of factor levels). when one or moreof these random factors are examined along with one or more fixed factors, a mixed model approach is neededto analyze such data. in this paper, we give a basic introduction of a two-way mixed effects model. Our mainfocus is to demonstrate how to use different procedures in SPSS and SAS to analyze such data