Many researchers are unfamiliar with suppressor variables and how they operate in multiple regression analyses. This paper describes the role suppressor variables play in a multiple regression model and provides practical examples that explain how they can change research results. A variable that when added as another predictor increases the total correlation coefficient squared (R squared) is a suppressor variable. Suppressor variables measure invalid variance in the predictor measures and...
Topics: ERIC Archive, Correlation, Predictor Variables, Regression (Statistics), Suppressor Variables,...
The important and sometimes difficult-to-grasp concept of regression suppressor variable effects is explored. An inquiry into the phenomenon of suppressor effects is accomplished via a synthesis of the existing literature and the use of a small heuristic data set to improve the accessibility of the concept. Implications for researchers are also forwarded and it is suggested that the search for suppressor variables in an effort to remove unwanted predictor variable variance may prove less...
Topics: ERIC Archive, Heuristics, Multiple Regression Analysis, Predictive Measurement, Predictor...
Suppressor effects are considered one of the most elusive dynamics in the interpretation of statistical data. A suppressor variable has been defined as a predictor that has a zero correlation with the dependent variable while still, paradoxically, contributing to the predictive validity of the test battery (P. Horst, 1941). This paper explores the three definitions of regression suppressor variables by reviewing existing literature about suppressor effects and provides a heuristic example that...
Topics: ERIC Archive, Correlation, Definitions, Heuristics, Identification, Predictor Variables,...
The purpose of this paper is to illuminate the advantages of path analysis for the exposition of results in data analytic papers. Probably the greatest advantage is that it provides a means by which the nature of the problem may be handily summarized. The method of path analysis, although conceived over sixty years ago by Sewell Wright, has only recently been introduced into educational literature. Its application in substantive analyses in education has also been infrequent. Path analysis...
Topics: ERIC Archive, Correlation, Critical Path Method, Data Analysis, Mathematical Models, Multiple...
The degree to which the chosen units of analysis are likely to produce spurious findings in staged combinations of multiple linear regression procedures are examined. The effects of grouping variables (e.g., classroom, school, and school district) on Procedures such as Coleman's semipartial regression and Mayeske's commonalities, in light of hypothetical sample homogeneity and heterogeneity are also illustrated. The utility of including grouping variables in the regression models and...
Topics: ERIC Archive, Analysis of Variance, Correlation, Data Analysis, Educational Research, Evaluation...
A Monte Carlo simulation was used to ascertain the degree of inflation that can occur in regression estimates when samples contain randomly occurring instances of a pattern among correlations called cooperative suppression. Ten thousand samples of scores on three variables were randomly drawn from a population in which the correlations among the variables were prespecified such that cooperative suppression did not exist. Cooperative suppression occurred in nearly 48% of the samples but the...
Topics: ERIC Archive, Correlation, Critical Path Method, Goodness of Fit, Hypothesis Testing, Mathematical...
Starting with laboratory research on the suppression of visualization in reading, this study investigates effects of treatments (reading vs. listening and pictures vs. no pictures, in a 2x2 design) and aptitudes on the learning of verbal and spatial types of content. Approximately 100 fifth grade pupils were given a battery of four ability tests, learning materials dealing with the heart and the flow of blood, and immediate post-tests to assess acquisition of verbal and spatial aspects of the...
Topics: ERIC Archive, Academic Aptitude, Aptitude Treatment Interaction, Attention, Foreign Countries,...
The suppressor variable, a variable wholly uncorrelated with a criterion, but which nevertheless improves prediction because of its relationship with a predictor, is critically examined. For a suppressor so defined, formal identities are shown with part, partial, and multiple correlational procedures. It is demonstrated that if maximum prediction is the primary goal, the use of the suppressor approach is appropriate if, and only if, the suppressor-criterion correlation is zero. Otherwise...
Topics: ERIC Archive, Analysis of Variance, Correlation, Criteria, Mathematical Concepts, Measurement...
When two groups, initially dissimilar, undergo different treatments, can subsequent differences be partitioned in such a way that the difference between the two treatments is unbiased? This is the central problem of this paper, and it is confronted by the examination of two levels of information using a Follow Through Evaluation. The first information level contains, in addition to outcome variables (achievement tests), information on child characteristics and family background. The second...
Topics: ERIC Archive, Achievement Tests, Analysis of Covariance, Analysis of Variance, Comparative...
