Analysis of cigarette purchase task instrument data with a left-censored mixed effects model

Wenjie Liao, Xianghua Luo, Chap T Le, Haitao Chu, Leonard H. Epstein, Jihnhee Yu, Jasjit S Ahluwalia, Janet L Thomas

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


The drug purchase task is a frequently used instrument for measuring the relative reinforcing efficacy (RRE) of a substance, a central concept in psychopharmacological research. Although a purchase task instrument, such as the cigarette purchase task (CPT), provides a comprehensive and inexpensive way to assess various aspects of a drug's RRE, the application of conventional statistical methods to data generated from such an instrument may not be adequate by simply ignoring or replacing the extra zeros or missing values in the data with arbitrary small consumption values, for example, 0.001. We applied the left-censored mixed effects model to CPT data from a smoking cessation study of college students and demonstrated its superiority over the existing methods with simulation studies. Theoretical implications of the findings, limitations of the proposed method, and future directions of research are also discussed.

Original languageEnglish (US)
Pages (from-to)124-132
Number of pages9
JournalExperimental and Clinical Psychopharmacology
Issue number2
StatePublished - Apr 2013


  • Cigarette purchase task
  • College smoking
  • Demand curve
  • Left-censored mixed effects model
  • Relative reinforcing efficacy


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