Psychometric properties of brief indexes designed to measure social-cognitive predictors of smoking initiation.
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.
Hansen
Pernille Envold
PE
Department of Psychosocial Cancer Research, Institute of Cancer Epidemiology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen Ø, Denmark. pernille@cancer.dk
Siersma
Volkert
V
Ross
Lone
L
Mortensen
Erik Lykke
EL
Riegels
Mette
M
Tjørnhøj-Thomsen
Tine
T
Johansen
Christoffer
C
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