Psychometric Assessment of the PPDG: Utilizing Cronbach's Alpha as a Means of Reliability

  • Lisa R Marr-Lyon
  • Gireesh V Gupchup
  • Joe R Anderson
Keywords: pharmacy practice, enhancing measurement understanding, directive guidance


Introduction: Since the development of the 10 item Purdue Pharmacist Directive Guidance (PPDG) Scale several studies of the psychometric properties of the PPDG have been conducted. Although Cronbach's alpha was calculated as a means of internal consistency reliability, a demonstration of the mean centering of the individual items from the instrument were not explored.

Objectives: This study focused on investigating the mean stabilization of items within the PPDG as they pertain to Cronbach's reliability coefficient calculation.

Methods: Using item analysis procedures in SPSS, the mean stability of items within the general factor of directive guidance and subscales of instruction and feedback and goal setting were examined for the PPDG.

Results: Mean stability scores for entire PPDG scale and the subscales of instruction and feedback and goal setting were strong. Also, corrected item-total correlations and Cronbach's alphas following item deletion were good for the overall PPDG scale and the subscales.

Conclusions: The results provide evidence to enhance understanding of the psychometric stability of the PPDG scale and its subscales.


Type: Original Research


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Received 2016-02-10
Published 2013-01-01
Pharmacy Practice & Practice-Based Research