A Comparison of School Mean Achievement Scores With Two Estimates of the Same Scores Obtained by the Item-Sampling Technique

The accuracy of estimating test means for groups of twelfth-grade students by the item-sampling technique was examined. The subjects were from 35 twelfth-grade schools participating in the National Longitudinal Study of Mathematical Abilities. Half of the students in each school were assigned to a treatment condition where they took a complete 24-item mathematics test on the first day of testing and took item-sampled versions of the same test on the second day of testing. A second random group of students within each of the schools took the item-sampled version of the mathematics test on day 2 but did not take the complete version of the mathematics test on day 1. There was no evidence to indicate that taking the complete 24-item mathematics test influenced the performance on the item-sampled version on the second day of testing. Reasonably close estimates of mean performance were obtained from the item-sampling situation as compared to the means estimated from the conventional type of testing. The differences between the means estimated from conventional type testing and from item-sampling testing were found to diminish as a function of the number of students tested in the school (square root transformation). (Author/PR)