Resource room students (N=68) in grades 1-7 of three rural and suburban Minnesota school districts participated in a study of time series data generated by a curriculum-based measurement system. A principal components factor analysis was performed to summarize relationships among the time-series properties and properties of the measurement system. In addition, multiple regression analyses were used to identify the relationship of such variables to achievement. Results indicated that the statistical characteristics of time-series data are not necessarily independent in naturally occurring data, and can be used in predicting achievement. Findings had implications in training practitioners in the use and interpretation of measurement systems based on time-series data. (Author/CL)