Figure 4From: Item response theory-based measure of global disability in multiple sclerosis derived from the Performance Scales and related items Relations among the levels of the Performance Scales Sum (PSS-11) score and the IRT summed score of global disability. Note: To facilitate comparisons, the levels of the IRT summed score were linearly transformed to range from 0 to 46 (i.e., the range of the PSS-11 levels). Thus, had the levels of the two scores been perfectly equivalent, then the dots on the figure would have been aligned on the diagonal line.Back to article page