A psychometric evaluation of 4-point and 6-point Likert-type scales in relation to reliability and validity

Abstract

Reliability and validity of 4-point and 6-point scales were assessed using a new model-based approach to fit empirical data. Different measurement models were fit by confirmatory factor analyses of a multitrait-multimethod covariance matrix. 165 graduate students responded to nine items measuring three quantitative attitudes. Separation of method from trait variance led to greater reduction of reliability and heterotrait-monomethod coefficients for the 6-point scale than for the 4-point scale. Criterion-related validity was not affected by the number of scale points. The issue of selecting 4- versus 6-point scales may not be generally resolvable, but may rather depend on the empirical setting. Response conditions theorized to influence the use of scale options are discussed to provide directions for further research. Index terms: Likert-type scales, multitrait-multimethod matrix, reliability, scale options, validity.