Construct validity of a mammography processes of change scale and invariance by stage of change.

The development and use of validated processes of change (POC) measures have received little attention in the literature despite their importance in the Transtheoretical Model. Using survey data (N = 2909), we examined the construct validity of a 22-item mammography POC scale by testing for factorial validity and factorial invariance across stage of change. We also used MANOVA with Tukey post-hoc tests to confirm stage differences in POC use (concurrent validity). Our results confirm the a priori correlated four-factor structure of this scale and provide some support for the measurement equivalence of this scale across stage, supporting comparisons of POC use across stage.