title: Intention-behavior relationship based on epidemiologic indices: an application to physical activity.
abstract: OBJECTIVE
  This article examines the usefulness of epidemiologic indices in furthering the understanding of the intention-behavior relationship in the field of physical activity.
  
  
  METHODS
  Six prospective data sets of physical activity were used.
  
  
  METHODS
  The United Kingdom and Canada in various settings (school, workplace).
  
  
  METHODS
  Different segments of the population (students, employees).
  
  
  METHODS
  Intention at baseline and behavior at follow-up, both assessed by means of questionnaires.
  
  
  METHODS
  Intention and behavior were dichotomized to create a 2 x 2 table; this allowed us to compute four standard epidemiologic indices: sensitivity, specificity, positive predictive value (PV+), and negative predictive value (PV-).
  
  
  RESULTS
  Sensitivity was 86.3%, which reflected the high sensitivity of intention for exercising, i.e., active individuals were very likely to hold a positive intention. Specificity was 49.5%, which suggested that a significant number of inactive individuals held a positive intention. With respect to predictive values, a low intention was a very good predictor of being inactive (PV- = 88.1%), whereas a positive intention was a moderate predictor of being active (PV+ = 45.5%).
  
  
  CONCLUSIONS
  These results indicate that intention is a moderate predictor of behavior and that the gap between intention and behavior is caused by high intenders not taking action. Health promotion programs would benefit to target factors that moderate the intention-behavior relationship.
authors.affiliation: Laval University, Québec, Canada. gaston.godin@fsi.ulaval.ca
authors.forename: Gaston
authors.initials: G
authors.lastname: Godin
authors.forename: Mark
authors.initials: M
authors.lastname: Conner
mesh_terms: D000293:Adolescent; D000328:Adult; D002170:Canada; D002648:Child; D015444:Exercise / Q000523:psychology*; D005260:Female; D015438:Health Behavior; D006801:Humans; D033182:Intention; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011594:Psychometrics; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D006113:United Kingdom