Assessing the Impact of Equating Error on Group Means and Group Mean Differences

Equating error is usually small relative to the magnitude of measurement error, but it could be one of the major sources of error contributing to mean scores of large groups in educational measurement, such as the year-to-year state mean score fluctuations. Though testing programs may routinely calculate the standard error of equating (SEE), the commonly used summary statistics of SEE are not direct quantifications of the impact of equating error on group means. This article proposed summary statistics that directly quantify the impact of equating error on group means or group mean differences and provided empirical and analytical methods to estimate these statistics. Examples based on empirical data were used to illustrate practical applications of these statistics.