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Explore the benefits of Item Response Theory (IRT) over Classical Test Theory (CTT) for analyzing student performance changes over time. IRT offers a modern, sophisticated approach that accommodates large sample sizes, providing valuable insights through item characteristic curves and equating procedures. Enhance your assessment strategies with IRT tools for accurate longitudinal evaluation.
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Using Item Response Theory to Track LongitudinalCourse Changes Charles H. Atwood, Braden Ohlsen, and Brock Casselman University of Utah Department of Chemistry Salt Lake City, UT
Quick Description of Item Response Theory (IRT) • Classical Test Theory (CTT) • Mean, median, mode • Discrimination Index • comparison of top and bottom quartiles • CTT is good for small samples • CTT is more dependent upon the subject group • Same assessment given to 2 groups will give different results
Quick Description of Item Response Theory (IRT) • Item Response Theory (IRT) • More modern psychometric analysis tool than CTT • Works well for large sample sizes (> 200) • Iterative process which fits the students responses to a mathematical formula
Quick Description of Item Response Theory (IRT) • We use the program Bilog-MG3 to fit our data. • Bilog-MG3 assigns to every test item values for a, b, and c and displays them on an item characteristic curve • Plot of the probability of a student with a given IRT ability vs. probability that the student answered the question
Quick Description of Item Response Theory (IRT) • Item Characteristic Curve
Description of Item Response Theory (IRT) • Item Information Curve for every test question
Description of Item Response Theory (IRT) • Test information curve • Sum of Item Information Curves for an assessment