title: Sum-of-products variables: a methodological critique.
abstract: Sum-of-products variables are integral to testing certain psychological theories (e.g., the theory of reasoned action). A sum-of-products variable is a total score computed by multiplying the scores for corresponding items from two scales and then adding the products. This type of variable is associated with methodological difficulties, however. The purpose of this article is to discuss certain methodological issues associated wtih the use of sum-of-products variables in health-related research.
authors.affiliation: School of Nursing, University of Wisconsin-Madison 53792-2455.
authors.forename: D
authors.initials: D
authors.lastname: Lauver
authors.forename: T R
authors.initials: TR
authors.lastname: Knapp
mesh_terms: D001290:Attitude; D006801:Humans; D015399:Nursing Research / Q000379:methods; D011594:Psychometrics / Q000379:methods*; D015203:Reproducibility of Results