Fig. 7
QUEST variable map (McKay 2000a p.220). This figure shows how the QUEST estimate develops a uni-dimensional (logit) scale (− 3.0 to 1.0) with equal intervals along each axis as it measures participants’ performances and test-items together. The x’s on the left hand side of the figure represent an individual participant’s performance with the total number of participants being 195. On the right hand side of the figure, is the difficulty rating of each test-item’s performance (partial credit scored test-items have multiple entries: 8.1, 8.2 and 9.3, 20.2)