This research assessed the reliability, presence of a proposed simplex pattern (construct validity), factorial validity, and multisample invariance of the Situational Motivation Scale (SIMS; Guay, Vallerand, & Blanchard, 2000). In Study 1, data were collected from three physical activity samples. After establishing internal consistencies for all scales, bivariate and interfactor correlations were calculated and the results supported a simplex pattern across samples. The SIMS factorial validity across the three samples was tested via confirmatory factor analysis. Based on modification indices and theoretical justification, the SIMS was reduced to a 14-item model and the multisample invariance of this solution was examined. Results supported partial invariance. In Study 2, a total of 1,008 female PE students responded to the SIMS under two experimental conditions. Internal consistency and the assumed simplex pattern was again supported. Finally, the results of multisample CFA were consistent with the proposed post hoc model respecifications suggested in Study 1, supporting partial invariance.
M. Standage, Dept of Sport & Exercise Science, Univ. of Bath, Bath BA2 7AY, U.K.; D.C. Treasure, Dept of Kinesiology, Arizona State Univ., Tempe, AZ 85287; J.L. Duda, School of Sport & Exercise Sciences, Univ. of Birmingham, Birmingham B15 2TT, U.K.; K.A. Prusak, Dept. of Physical Education, Brigham Young Univ., Provo, UT 84602.