The following notes are intended to explain some of the more technical aspects of the research findings discussed in this book. These notes, however, are brief treatments of the topics addressed. For more detailed discussion, consult standard statistics textbooks, such as Cohen (1988); Cohen and Cohen (1975); Glass, McGaw, and Smith (1981); Glass, Willson, and Gottman (1975); and Hunter and Schmidt (1990).

Technical Note 1

One of the most common indices found in the research literature is the percent of variance explained (or PV). A basic assumption underlying the use of this index is that the percentage of variance explained by a predictor (or independent) variable (e.g., schooling) relative to a predicted (or dependent) variable (e.g., student achievement) represents the strength of relation between the two. Most commonly, a “set” of predictor variables is used.