Annals of Behavioral Medicine

, Volume 50, Issue 5, pp 751–761 | Cite as

Baseline Characteristics and Generalizability of Participants in an Internet Smoking Cessation Randomized Trial

  • Sarah Cha
  • Bahar Erar
  • Raymond S. Niaura
  • Amanda L. Graham
Original Article



The potential for sampling bias in Internet smoking cessation studies is widely recognized. However, few studies have explicitly addressed the issue of sample representativeness in the context of an Internet smoking cessation treatment trial.


The purpose of the present study is to examine the generalizability of participants enrolled in a randomized controlled trial of an Internet smoking cessation intervention using weighted data from the National Health Interview Survey (NHIS).


A total of 5290 new users on a smoking cessation website enrolled in the trial between March 2012 and January 2015. Descriptive statistics summarized baseline characteristics of screened and enrolled participants, and multivariate analysis examined predictors of enrollment. Generalizability analyses compared demographic and smoking characteristics of trial participants to current smokers in the 2012–2014 waves of NHIS (n = 19,043) and to an NHIS subgroup based on Internet use and cessation behavior (n = 3664). Effect sizes were obtained to evaluate the magnitude of differences across variables.


Predictors of study enrollment were age, gender, race, education, and motivation to quit. Compared to NHIS smokers, trial participants were more likely to be female, college educated, and daily smokers and to have made a quit attempt in the past year (all effect sizes 0.25–0.60). In comparisons with the NHIS subgroup, differences in gender and education were attenuated, while differences in daily smoking and smoking rate were amplified.


Few differences emerged between Internet trial participants and nationally representative samples of smokers, and all were in expected directions. This study highlights the importance of assessing generalizability in a focused and specific manner.



Smoking cessation Internet Research design 


Compliance with Ethical Standards


This study was supported by funding from the National Cancer Institute of the National Institutes of Health (#5R01CA155489). The study is registered at (NCT01544153).

Conflict of Interest

Sarah Cha, Raymond S. Niaura, and Amanda L. Graham are employees of Truth Initiative, a non-profit public health foundation that runs, an online tobacco cessation intervention.

Supplementary material

12160_2016_9804_MOESM1_ESM.docx (36 kb)
ESM 1(DOCX 36 kb)


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Copyright information

© The Society of Behavioral Medicine 2016

Authors and Affiliations

  • Sarah Cha
    • 1
  • Bahar Erar
    • 2
  • Raymond S. Niaura
    • 1
    • 3
  • Amanda L. Graham
    • 1
    • 4
  1. 1.Schroeder Institute for Tobacco Research and Policy StudiesTruth InitiativeWashingtonUSA
  2. 2.Center for Statistical SciencesBrown UniversityProvidenceUSA
  3. 3.Department of Health, Behavior and SocietyThe Johns Hopkins Bloomberg School of Public HealthBaltimoreUSA
  4. 4.Department of OncologyGeorgetown University Medical Center/Cancer Prevention and Control Program, Lombardi Comprehensive Cancer CenterWashingtonUSA

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