title: Dispositional optimism is unidimensional or bidimensional? The Portuguese revised Life Orientation Test.
abstract: The aim of the study is to adapt and then discuss the appropriateness of the Life Orientation Test as a one or two dimension scale. The research includes two studies; one is composed of a sequential sample of 280 people with multiple sclerosis, 71% female, and another includes a convenience sample of 615 individuals from the community, 51.1% female. Because the construct is built upon a theoretical assumption that has one dimension, we examine the hypothesis of one or two factor solutions through confirmatory factor analysis, and the two-dimension solution premise demonstrates better adjustment for both samples. The other psychometric properties explored show appropriate results for the Portuguese sample, and similar to the original ones; the Test therefore seems appropriate for use in cross cultural studies. Based on our results, we discuss whether the questionnaire is a one or two dimension instrument, concluding that it appears appropriate to accept the recommendations of the original authors to use it as a one-dimensional tool and, when necessary, to use both dimensions.
authors.affiliation: Universidade do Porto, Rua do Dr. Manuel Pereira da Silva, 4200-392 Porto, Portugal. jlpr@fpce.up.pt
authors.forename: Jose Luis Pais
authors.initials: JL
authors.lastname: Ribeiro
authors.forename: Luis
authors.initials: L
authors.lastname: Pedro
authors.forename: Susana
authors.initials: S
authors.lastname: Marques
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000175:diagnosis / Q000523:psychology; D009949:Orientation; D010551:Personality / Q000502:physiology*; D011174:Portugal; D011594:Psychometrics / Q000295:instrumentation* / Q000592:standards; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards*; D055815:Young Adult