Rack and Stack

The Structure and Stability of the Functional Independence Measure (FIM) http://www.rasch.org/memo50.htm Cites sources regarding deficiencies of raw score analysis of scales http://www.rasch.org/rmt/rmt103e.htm Defends use of Rasch to analyze these data for a critic

This concept can be applied elsewhere Comparing people over time (how much people improve after intervention) Comparing items over time (how much easier items become after intervention) “Rack and Stack” Example: www.raschsig.org/rmt171.pdf

To look at person change: Stack Items are modeled to maintain their difficulties across the two time points, and the persons are entered twice, once at admission to rehabilitation and once at discharge from it. Changes in patient independence can be identified by cross-plotting the admission and discharge measures for each patient, as in example 12 or looking at the difference in measures Persons Items Persons (again) Time 1 Time 2

To look at item change: Rack To look at WHAT has changed instead of WHO has changed. Items are entered twice, once at admission to rehabilitation and once at discharge from it. Items Items (again) Time 1 Time 2 Persons