1. What is the difference between the reliability and validity of a measurement? The validity of a measure is the extent to which differences in scores on the instrument reflect true differences among ...

Several conceptions of validity have emphasized the contingency of validity on theory. Here we revisit several contributions to the discourse on the concept of validity, which we consider particularly ...

Objectives To compare the construct validity, including discrimination between known groups, of three pain and three morning stiffness (MS) measurement instruments. Methods Patients with radiographic ...

Objectives The Disease Activity index for Psoriatic Arthritis (DAPSA) was developed to assess disease activity in patients with psoriatic arthritis (PsA). A modified version, DAPSA28, uses 28 joints ...