This macro, introduced in November 2019, allows for test items to be investigated to see if they might fit the Rasch Model.

 

Tests must involve cognitive items scored on a right/wrong basis. That is to say, the macro is exclusively for use with "dichotomous" test items (at least at the moment).

 

This excellent example by Mark Moulton explains how the macro works.

 

Examples of the macro's output are shown below. They're based on test results collected from students in Japan as part of the FIMS project.

 

SampleRaschOutputFIMS-Japan  

 

RaschAnalysis1-sampleoutput3

 

Note that the macro has centered the item difficulty estimates, "Rasch Diff", at zero (the average difficulty is 0.00 as shown above). This is in keeping with the Rasch examples used in the Bond & Fox texts: "Applying the Rasch Model" (references are here).

 

Red highlighting is used to draw attention to item INFIT and OUTFIT values which may be less than or greater than desired.

 

values less than 0.7 will be in red no matter what the sample size (number of students)

values greater than 1.1 will be in red when sample size is 1000 and above

values greater than 1.2 will be in red when sample size is between 500 and 1000

values greater than 1.3 will be in red when there are less than 500 students

 

When all iterations have been completed, the student (person) INFIT and OUTFIT values produced by the macro will be found, along with Rasch scores, in the Scores worksheet. When these values are less than 0.75, or greater than 1.3, they are highlighted in red (no matter what the sample size might be). The Sort option may be used to have a closer look at the range of these values and scores.

 

Some of the examples in Bond & Fox are based on the "BLOT" test. The next page compares the macro's output with that published on p.56 of Bond & Fox (2007).