title: Psychometric properties of brief indexes designed to measure social-cognitive predictors of smoking initiation.
abstract: BACKGROUND
  Constructing indexes which measure factors that may predict smoking initiation is essential for planning prevention programs. Our aim was to examine the criterion-related construct validity of brief psychological indexes of attitude, social influence and self-efficacy to be used in future studies for predicting smoking initiation in adolescents.
  
  
  METHODS
  Five indexes were evaluated using cross-sectional data on 4819 adolescents age 13 in a random sample of schools in six Danish counties. Item analyses were performed with the graphical log-linear Rasch model, a modification of the Rasch model that allows for differential item functioning and positive local dependence.
  
  
  RESULTS
  The three indexes social influence-norms, social influence-pressure and attitude showed acceptable deviations from the Rasch model, while the two indexes self-efficacy and social influence-behavior were invalidated by negative local dependence.
  
  
  CONCLUSIONS
  Of the five tested indexes, three (social influence-norms, social influence-pressure and attitude) showed acceptable criterion-related construct validity and may be considered unbiased representations of the theory-based factors if statistical analyses are appropriately adjusted. The results of this population-based study show that the graphical log-linear Rasch model is useful for evaluating health-related behavior indexes and identifying problems, which can be dealt with when using the indexes in future studies.
authors.affiliation: Department of Psychosocial Cancer Research, Institute of Cancer Epidemiology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen Ø, Denmark. pernille@cancer.dk
authors.forename: Pernille Envold
authors.initials: PE
authors.lastname: Hansen
authors.forename: Volkert
authors.initials: V
authors.lastname: Siersma
authors.forename: Lone
authors.initials: L
authors.lastname: Ross
authors.forename: Erik Lykke
authors.initials: EL
authors.lastname: Mortensen
authors.forename: Mette
authors.initials: M
authors.lastname: Riegels
authors.forename: Tine
authors.initials: T
authors.lastname: Tjørnhøj-Thomsen
authors.forename: Christoffer
authors.initials: C
authors.lastname: Johansen
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D001294:Attitude to Health; D003071:Cognition; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005544:Forecasting; D006801:Humans; D008297:Male; D008960:Models, Psychological; D011594:Psychometrics; D015203:Reproducibility of Results; D020377:Self Efficacy; D012907:Smoking / Q000453:epidemiology / Q000523:psychology* / Q000639:trends*; D012931:Social Environment