The Use of Generalizability Theory in Examining the Dependability of Scores on the Profile of Mood States

The dependability of the Profile of Mood States (POMS) is examined in several different ways and, in doing so, illustrates the flexibility of Generalizability theory. One issue evaluated is the impact of changing the design by sampling more dimensions of mood disturbance, or by increasing the numbers of items per subscale. The second issue examined is the impact of considering scales as fixed effects versus random effects. Each of the POMS' 6 subscales displayed reasonably high G coefficients (ξρ ≥ .74). The generalizability of the overall Total Mood Score (TMS) was found to be fairly high (-.90), even if scales were treated as random. In the random case, generalizability would tend to increase modestly if the number of scales were increased, and would increase very little if the number of items per scale were doubled. Treating subscales as fixed had a substantial positive impact on the dependability of the TMS, yielding a G coefficient of .96.