Figure 2

Person-Item Threshold Response Map for the WOMAC Physical Functioning subscale (pre-data). The graph displays the person-item threshold distribution map with the x-axes displaying location or difficulty of item thresholds (lower half) and location or level of physical functioning reported by participants (upper half). The y-axes display the frequencies of item thresholds (lower half) and participants (upper half). Data for this figure represent the unbiased person estimates derived from Analysis 2 (see also Table 2) which combined biased items 1 and 5 into a testlet and left the remaining items are unchanged.