Psychometric Properties of the Multidimensional Schizotypy Scale and Multidimensional Schizotypy Scale-Brief: Item and Scale Test-Retest Reliability and Concordance of Original and Brief Forms.

We conducted 2 studies examining the psychometric properties of the Multidimensional Schizotypy Scale (MSS) and the Multidimensional Schizotypy Scale-Brief (MSS-B). These studies offered the first examination of the scales' test-retest reliability (dependability), impact of testing interval on test-retest reliability, and concordance of the 2 versions. The MSS and MSS-B contain positive, negative, and disorganized schizotypy subscales that reflect current models of schizotypy. In Study 1, MTurk participants (n = 245) completed the scales at 2 assessments across a 7-week time interval. Test-retest reliabilities (intraclass correlations) ranged from .84 to .90 for the MSS subscales and from .77 to .85 for the MSS-B subscales, and were unaffected by the interval length between administrations. The association between the same subscales of the MSS and MSS-B across the 2 assessments ranged from .79 to .87, indicating good correspondence between the MSS and MSS-B. Scores on the MSS-B subscales in Study 1 were derived from the full-length MSS. Therefore, we replicated the findings using the actual MSS-B subscales in Study 2 in 3 samples (total n = 339). The results indicated that the MSS and MSS-B have good internal consistency and test-retest reliabilities (dependability), and that there is high concordance between the full-length and brief versions.