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Fig. 1 | Journal of Patient-Reported Outcomes

Fig. 1

From: Psychometric performance of the PROMIS® depression item bank: a comparison of the 28- and 51-item versions using Rasch measurement theory

Fig. 1

Scale-sample targeting: top histograms (pink bars): sample’s distribution of depression measurements (person locations) measured by the PROMIS 51 items in (a) and the PROMIS 28 in (b). Person measurements reflecting lower ability (lower depression) are represented by histogram bars on the left and person measurement reflecting higher ability (higher depression) by the histogram bars on the right. Lower histograms (blue bars): scale distribution of item threshold location estimates for the 51 items in (a) and the 28 items in (b). Histogram bars on the left represent the easiest items (requiring lower levels of depression to be positively endorsed) and histogram bars on the right represent the more difficult items (requiring higher levels of depression to be positively endorsed). Green curve: represent an inverse function of the standard error associated with measurement, it reflects scale’s precision and shows the location on the continuum the scale performs at its best, indicating that the location of item thresholds and persons is well matched

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