IRT Ability-vs-Difficulty Explorer¶
Run the IRT Explorer Fullscreen Edit Using the p5.js Editor
About This MicroSim¶
This MicroSim plots the Item Response Theory logistic curve. The x-axis shows learner ability (theta, -4 to +4) and the y-axis shows probability of a correct response (0 to 1). A vertical line marks item difficulty, a horizontal line marks probability at the current ability, and their intersection is highlighted.
Controls:
- Ability (theta) -- learner ability from -4 to +4
- Difficulty (b) -- item difficulty from -4 to +4
- Show 2PL -- adds a discrimination parameter (a) that controls the curve's steepness
- Show Information Curve -- overlays the item information function, which peaks where theta = b
- Reset -- restores defaults
The caption labels three qualitative zones: "too easy" (P > 0.85), "at the edge of ability" (0.5 to 0.85), and "too hard" (P < 0.35).
Learning Objective (Understand): Using the IRT explorer, explain why an item calibrated near the learner's ability yields the most information per unit of testing time.