Assessment of Test Items with Rasch Measurement Model.

The study was carried out to assess the difficulty index of each item of an Economics Achievement test with the Rasch model. The infit and outfit as well as the reliability of the test were determined. Three research questions were drawn to guide the study. A sample of 200 was randomly selected using simple random sampling of balloting and proportionate stratified random sampling. The instrument of the study was an Economics Achievement Test with 100 items. The test has face and content validities. It has a reliability coefficient of 0.86 established through the use of Kuder-Richardson 20 method. A Rasch model software of Winsteps version 3.75 was used to analyse the data collected. The result identified the difficulty index of each item. The infit and outfit of both MNSQ and ZSTD were determined. The reliability of the Economics Achievement Test was estimated. It was recommended among others that Rasch model should always be used in assessing the item difficulty of a test and ensure the stability of item parameters.