Estimating Trend in Progress Monitoring Data: A Comparison of Simple Line-Fitting Methods

Abstract

Four simple line-fitting procedures are presented for practitioners to quickly summarize student time series performance data. Two are in common use — Koenig's “quarter-intersect” and White's “split-middle” adjustment, while two — Tukey I and Tukey II — are less known. Each of the four can be performed on a medium-size classroom dataset in less than 3 minutes. The four procedures were assayed against three criteria: (a) matching line slopes to an ordinary least squares (OLS) standard; (b) “best fit” to the data (minimizing residuals); and (c) prediction of a future reading score at Week 16. Weekly oral reading fluency data were collected on 45 Grade 4 and 5 students with reading disabilities, over a period of 12 weeks. Tukey I and II techniques generally outperformed the Koenig and White line-fitting methods, especially White's “split-middle” adjustment. Performance differences were generally large enough to be educationally meaningful. Given the small database supporting the popular White and Koenig procedures, the authors recommend that practitioners cautiously try out Tukey I and II procedures, comparing results with Koenig's and White's procedures. Of course, further psychometric studies of all four procedures are needed also. The authors discuss three notable study limitations: limited generalizability, use of the future score prediction criterion, and no instructional use of the best-fit lines.

Additional information

Notes on contributors

Richard Parker

Richard Parker, PhD, is Assistant Professor of Educational Psychology, Special Education Area, at Texas A&M University. His research interests include classroom-based assessment, program evaluation, and school-wide interventions for students at-risk and with disabilities. He is currently studying problems of low achievement and dropout among Hispanic and African-American students in Texas schools.

Gerald Tindal

Gerald Tindal, PhD, is Associate Professor of Special Education at University of Oregon and director of the Consultation Training Program there. His active research interests include consultation effectiveness, assessment of higher order thinking skills, and other forms of classroom-based assessment. He recently authored a text on assessment for teachers.

Stephanie Stein

Stephanie Stein, PhD, is Assistant Professor of Psychology at Central Washington University. She is currently researching effective IEPs and classroom interventions for students with learning and behavior problems.