ORGANIZATIONAL RESEARCH METHODS Ganzach et al. / LINEAR VERSUS LOGISTIC MODELS Interaction in Linear Versus Logistic Models: A Substantive Illustration Using the Relationship Between Motivation, Ability, and Performance YOAV GANZACH ISHAK SAPORTA Tel Aviv University YAACOV WEBER The Hebrew University of Jerusalem A binary performance measure (high school graduation) is examined as a function of motivation (educational goal), ability (scores in an intelligence test), and their interaction. The interaction was positive when a logistic model was used and neg- ative when a linear probability model was used. The reason for the difference in the results of the two models is examined, and the conditions under which this dif- ference occurs are discussed. Many of the important dependent variables in organizational research are binary. For example, between 1995 and 1997 about 5% of the articles in the Journal of Applied Psychology and about 8% of the articles in the Academy of Management Journal used binary dependent variables. Nevertheless, methodological issues associated with the modeling of such variables, and, in particular, the modeling of interaction effects among their determinants, have received little attention in the literature. The purpose of this article is to examine issues associated with the modeling of interaction when the dependent variable is binary within the context of an important, yet little researched, substantive issue: The relationship between motivation and ability in the determina- tion of performance. A binary performance measure (high school graduation) is exam- ined. Scores in a cognitive ability test are used as a measure of ability, and educational goal is used as a measure of motivation. The article is organized as follows. We first review the relevant literature regarding (a) the modeling of binary dependent variables using linear and logistic models, and (b) the relationship between motivation, ability, and performance. We then present data showing that modeling performance as a function of motivation and ability by a linear probability model and modeling it by a logistic model lead to diametrically opposite conclusions about the interaction between motivation and ability. In the last Organizational Research Methods, Vol. 3 No. 3, July 2000 237-253 © 2000 Sage Publications, Inc. 237