ERIC Number: ED189099
Record Type: Non-Journal
Publication Date: 1978-Jun
Reference Count: N/A
Everything You Wanted to Know about the Rasch [Model] (But Were Afraid to Ask). Portland Public Schools Occasional Papers in Measurement No. 17.
Criticisms of norm referenced standardized tests are contrasted with the assumption and claims of proponents of Rasch model testing and item banking. The Rasch test theory model is based on the assumption of equal interval curriculum referenced scales for both students' abilities and test item difficulties. The Portland school district has established eight forty-item achievement tests, each covering only a short range of achievement, but all linked to a single ability scale. It is also possible to construct special purpose tests by selecting items from the item bank, since all items are keyed to achievement goals. Among the advantages of using the Rasch model are that you don't need representative samples for item analysis, and scores on the Rasch ability scale have tolerance values to indicate the expected size of measurement errors. The Portland school district has conducted a number of experiments with Rasch Statistics and concluded that samples of 200 cases are sufficient for item analysis, and to estimate the accuracy of the equating across ability levels. Work on additional curriculum areas and on rapid and meaningful score reporting is being developed. (CTM)
Publication Type: Guides - Non-Classroom; Opinion Papers
Education Level: N/A
Authoring Institution: Portland Public Schools, OR.