Calculates the absolute probability difference between a True Master answering correctly and a Non-Master guessing correctly. This is the Item-level equivalent of Gate Strength.
Usage
calc_item_discrimination_index(results, item)
Arguments
- results
The full pgdcm results list object.
- item
A string item ID or integer index.
Value
A list containing the target item, posterior mean gap, and 95
Semantic Interpretation
* **High Value (> 0.6)**: The item discriminates incredibly well. Masters are vastly more likely to get it right than non-masters.
* **Low Value (< 0.2)**: A weak item. Masters and non-masters have practically the same chance of answering correctly.
