Assessing Growth in Young Children: A Comparison of Raw, Age-Equivalent, and Standard Scores Using the Peabody Picture Vocabulary Test

Abstract

Many tests provide users with several different types of scores to facilitate interpretation and description of students’ performance. Common examples include raw scores, age- and grade-equivalent scores, and standard scores. However, when used within the context of assessing growth among young children, these scores should not be interchangeable because they provide different information. To examine how raw, age-equivalent, and standard scores function when assessing growth among young children, this article uses scores on the Peabody Picture Vocabulary Test–Third Edition to compare the use of these scores for the purpose of measuring growth in receptive vocabulary skills among a sample of 259 low-income, predominantly Hispanic preschoolers age 3 to 5 years. Results suggest a notable floor effect in the distribution of age-equivalent scores that was not observed in the raw score or standard score distributions. This floor effect may significantly affect the results of correlational data analyses conducted with these scores. In light of these findings and combined with a trend in the literature in which researchers often do not provide a clear rationale for choosing which test scores to use in statistical analyses, the authors offer suggestions for researchers when using test scores as dependent variables.