The purpose of this study was to develop an effective way to get equivalent groups for equating purposes using a matched-sample method, and to compare equating results obtained by using matched samples with equating results obtained by using a common-person design. The results of this study show that an equating parameter derived from the matched-sample method is very close to an equating parameter derived from a common-person design: the difference between the two designs is only about 0.1 scaled score unit (mean 400; standard deviation 25). In the paper, we consider the theoretical assumptions that support using the matched-sample method to determining equivalent groups and discuss the practical operations involved in using this method. Our findings suggest two major advantages to using the matched-sample method as compared to a common-person design. First, the data available to use with the matched-sample method comes from a large sample size, which makes the results more accurate and reliable than would be the case with a smaller sample size, which is often for common person design. The second advantage is that because we are able to use existing data with the matched-sample method, we do not need any extra design and operational efforts to collect common person data, which saves the time and money involved in conducting a research study in the field. For these reasons, we recommend using the matched-sample method whenever existing data is available, especially for renorming an existing test. |