This paper presents an analysis of the factors influencing human decision making, and its implications for the judgments and choices that result from juxtaposition of data with decision content. The analysis serves as a background for the consideration of selected issues regarding the specificity of information in data-based decision making in schools. The text is divided into the following sections: (1) reasons for focussing on specificity of information during the course of the Systemic Evaluation (SE) Project; (2) issues that influence the choice of appropriate specificity of information in data-based decision making in schools; (3) application of points raised during general analysis to the work on instructional information systems; (4) examples from existing practice illustrate specificity choices; and (5) suggestions intended to advance the state of practice with regard to balancing the competing factors that impinge the choice of specificity in data-based decision making in schools. (LMO)