Item Response Theory analysis of the Autonomy over Tobacco Scale (AUTOS)

Introduction: The Autonomy over Tobacco Scale (AUTOS) is composed of 12-symptoms of nicotine dependence. While it has demonstrated excellent reliability and validity, several psychometric properties have yet to be investigated. We aimed to determine (1) whether items functioned differently across demographic groups, (2) the likelihood that individual symptoms would be endorsed by smokers at different levels of diminished autonomy, and (3) the degree of information provided by each item and the reliability of the full AUTOS across the range of diminished autonomy. Methods: Data for this study come from two convenience samples of American adult current smokers (n = 777; 69% female; 88% white; Mage = 34 years, range: 18-78), of whom 66% were daily smokers (Mcigarettes/smoking day = 10.1, range: <1-70). Participants completed the AUTOS online as part of "a research study about the experiences people have when they smoke." Results: After p value correction, items remained invariant across sex and minority status, while two items functioned differently according to age, with minimal impact on the total AUTOS score. Discriminative power of the items was high. The greatest amount of information is provided at just under one-half SD above the mean and the least at the extremes of diminished autonomy. The AUTOS maintains acceptable reliability (>0.70) across the range of diminished autonomy within which more than 95% of smokers' scores could be anticipated to fall. Conclusion: The AUTOS is a versatile and psychometrically sound instrument for measuring the loss of autonomy over tobacco use. (C) 2015 Elsevier Ltd. All rights reserved.