Investigation of confirmatory factor structure, validity and reliability of reward probability index among students of senior high school in Tehran

Reward deficiency syndrome is the root of many mental disorders and behavioral problems. Long–term experience of failed paths to positive reinforcement act as unconditional stimuli for humans and other organisms. These experiences evoke emotional components such as depression and anxiety. The purpose of this research was to investigate the psychometric properties and confirmatory factor structure of reward probability index among students of senior high school in Tehran.

The method of this research is a type of psychometric validation studies. The statistical population included all senior high school students of public schools in Tehran. 364 students were selected as the sample using multi-stage cluster sampling method. Students were asked to complete Reward Probability Index (RPI), the Yale–Brown obsessive-compulsive scale modified for body dysmorphic disorder (BDD-YBOCS) and multidimensional scale of perceived social support (Zimet et al).

The results of confirmatory factor analysis showed that the two-factor model of reward probability index (reward probability and environmental suppressors) has a good fit. The total reliability coefficient of the questionnaire and the reward probability and environmental suppressor’s subscales were obtained by Cronbach’s alpha method of 0.90, 0.88 and 0.83, respectively. This indicates the appropriate reliability of the tool. This scale showed a significant correlation with the multidimensional scale of perceived social support by Zimet et al and the Yale–Brown obsessive-compulsive scale modified for body dysmorphic disorder. This correlation confirmed the convergent validity of the questionnaire.

The results indicate that the reward probability index scale has appropriate validity and reliability among students in Iranian society and could be used in psychological studies.