CAT 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This tutorial is OUTDATED.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 questions, 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_cat_response_table'
Various stopping rules, or combinations of stopping rules, can be used to decide when to end the test.
Tips to Use Node
The node uses a 4PL IRT model. If you want to only use 2 PL then set all c (guessing parameter) values to 0 and all d (inattention parameter) values to 1. If you want to use 1 PL then the value of a (discrimination parameter) depends on the model you're using. You could set it to 1.7 (see: http://www.rasch.org/rmt/rmt193h.htm). The b parameter (difficulty) is on the z-scale, so -3 means very easy and 3 means very difficult.
If you're new to CAT, the Psychometrics Centre runs 3-day courses teaching IRT, CAT and Concerto, see: IRT and CAT using Concerto (3 days)