Applies to tests, rating scales and questionnaires.
1. Draw a line representing the variable of intention and mark it with an arrow indicating "more" of the attribute.
2. Determine the characteristics of the highest and lowest persons for whom the test is intended.
3. Construct the "germ" of an item for each extreme person identified. The "germ" of an item is the basic idea in capsule form. At this point do not waste time composing an item in detail; just construct its embryonic form. Place the item-germs at the ends of the variable line.
4. Generate an item-germ for the middle of the variable followed by one between the middle one and each extreme.
5. Continue to develop the construct by generating an item-germ between each of the two previous ones across the full range of the variable to as many divisions as reasonable. A good way to build the variable from this point on is to write the item-germs on 3x5 index cards. The cards can be arranged in order, coded and revised as necessary.
6. Decisions about item-germ placement can be determined by having "experts" arrange the item-germs in order along the variable of interest. Give them several item-germs whose locations are already known together with other item-germs to be placed. A paired-comparisons approach can be used to systematically determine item-germ locations.
7. The initial arrangement of the item-germs provides a map of the intended variable. Its validity is based upon the degree of consensus among content experts.
8. Now construct well-composed items from the item-germs. Each item should be clearly worded and free from ambiguity.
9. Try out the items with one or more persons. Have them "take the test aloud" by commenting to you as the they read, interpret and answer the items. Try out the new version with other people. After several individual try-outs, each item should now be doing its intended job.
10. Administer the test to a relevant sample and compute the Rasch measures and fit statistics.
11. The measures and calibrations mark out a map of the variable. When demographic information is coded for items and persons, these characteristics can also be located on the map. This map is a commentary on the construct validity of the variable.
12. The correspondence between the intended map of the variable and the sample-generated map reflects the quality of the knowledge used in constructing the variable. A map of the intended variable will be confirmed by empirical evidence when the theoretical basis is well-founded and the item-writer is competent.
Adler School of Professional Psychology
Steps in Item Construction. Stone M. H. Rasch Measurement Transactions, 1997, 11:2 p. 559.
|Rasch Measurement Transactions (free, online)||Rasch Measurement research papers (free, online)||Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch||Applying the Rasch Model 3rd. Ed., Bond & Fox||Best Test Design, Wright & Stone|
|Rating Scale Analysis, Wright & Masters||Introduction to Rasch Measurement, E. Smith & R. Smith||Introduction to Many-Facet Rasch Measurement, Thomas Eckes||Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, George Engelhard, Jr.||Statistical Analyses for Language Testers, Rita Green|
|Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar||Journal of Applied Measurement||Rasch models for measurement, David Andrich||Constructing Measures, Mark Wilson||Rasch Analysis in the Human Sciences, Boone, Stave, Yale|
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