A generalizability study of the Norwegian version of KINDL in a sample of healthy adolescents.
OBJECTIVE
The aim in the present study was to illustrate generalizability theory by exploring some psychometric aspects of the Norwegian version of KINDL (KINDL-N). This questionnaire is a measure of quality of life in adolescents. It consists of 24 items arranged in six subscales or aspects, corresponding to six domains of adolescents' health-related quality of life.


METHODS
A total of 239 healthy adolescents completed the questionnaire. The analysis was performed in line with generalization theory, and this analysis yields among other things so-called generalizability and dependability coefficients, which are analogous to reliability coefficients in classical test theory. The preferred design was a mixed two-facet design, with the six aspects as a fixed facet and the items nested within aspects as a random facet. For comparison, a random two-facet design and a one-facet design were also analyzed.


RESULTS
The generalizability and dependability coefficients for KINDL-N are satisfactory, but the coefficients can be markedly improved by increasing the length of the instrument while keeping it to a manageable size. The mixed two-facet design resulted in somewhat higher coefficients than a one-facet design and much higher coefficients than a random two-facet design.


CONCLUSIONS
If the items within a questionnaire are arranged in distinct subscales, a two-facet design analyzed by generalizability theory gives more sophisticated results than classical test theory. Moreover, the results may depend considerably on whether a mixed or random two-facet design is chosen. Hence, the choice of an appropriate measurement design in line with the intended use of the questionnaire is essential.
Christophersen
Knut-Andreas
KA
Institute of Political Science, University of Oslo, Box 1097, Blindern, 0381, Oslo, Norway. k.a.christophersen@stv.uio.no
Helseth
Sølvi
S
Lund
Thorleif
T
D000293:Adolescent; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D009664:Norway; D011594:Psychometrics / Q000295:instrumentation*; D011788:Quality of Life / Q000523:psychology*; D011795:Surveys and Questionnaires / Q000592:standards*