polyCAT Test node - campsych/concerto-platform GitHub Wiki

This tutorial is OUTDATED. It applies to Concerto releases up to v5.0.beta.7.

Purpose of Node

To present polytomous questions (using Likert responses), one at a time, using a CAT algorithm to choose the next item and IRT to do the scoring.

By default, data is stored in the 'default_polycat_response_table'

Various stopping rules, or combinations of stopping rules, can be used to decide when to end the test.

Tips to Use Node

Threshold Parameters

There are more spaces for threshold parameters than are required (e.g. in the PCM model you need 1 fewer threshold parameter than number of response options - so if you have 4 response options you'll have 3 threshold parameters). In the Concerto table, the first threshold parameter should be blank. So if you had 4 response options then the parameters would be something like this:

"blank", -.5, 0, 0.5

Disordered Thresholds

If you have disordered thresholds, then you should give both thresholds the same parameter value, e.g:

"blank", -.5, 0, 0

Notice that the last two response options have the same threshold parameter (0). No matter whether the user chooses option 3 or 4 their theta/sem will be calculated to be the same.

Examples