Further observations on the psychometric properties of the Psychological Effectiveness Scale

Previous work by Poe and by the present writer have shown that the Psychological Effectiveness Scale (PES) has sufficiently high validity and reliability to justify continued research on the instrument. In an attempt to study further the psychometric attributes of the PES, 54 American men and women volunteer methadone clinic patients were assigned a wider range of rating tasks than had hitherto been used. The Ss rated themselves under six different instructions. Internal consistency reliability, measured by coefficient alpha, was in the .90s in all ratings. The differences between the means of some of the ratings were significant at the .01 level. Average item-correlation (total minus item) was also high. These findings, consistent with the results of earlier work, confirm the reliability and construct validity of the PES.