Caffeine expectancy: instrument development in the Rasch measurement framework.

Although caffeine is the most widely consumed psychoactive drug in the world, the mechanisms associated with consumption are not well understood. Nonetheless, outcome expectancies for caffeine use are thought to underlie caffeine's reinforcing properties. To date, however, there is no available, sufficient measure by which to assess caffeine expectancy. Therefore, the current study sought to develop such a measure employing Rasch measurement models. Unlike traditional measurement development techniques, Rasch analyses afford dynamic and interactive control of the analysis process and generate helpful information to guide instrument construction. A 5-stage developmental process is described, ultimately yielding a 37-item Caffeine Expectancy Questionnaire (CEQ) comprised of 4 factors representing "withdrawal symptoms," "positive effects," "acute negative effects," and "mood effects." Initial evaluation of the CEQ yielded sufficient evidence for various aspects of validity. Although additional research with more heterogeneous samples is required to further assess the measure's reliability and validity, the CEQ demonstrates potential with regard to its utility in experimental laboratory research and clinical application. 2009 APA, all rights reserved.