Likert or Rasch? Nothing is more applicable than good theory

Abstract

In nursing research many concepts are measured by questionnaires. Respondents are asked to respond to a set of related statements or questions. In unidimensional scaling these statements or questions are indicants of the same concept. Scaling means to assign numbers to respondents, according to their position on the continuum underlying the concept. It is very common to use the summative Likert scaling procedure. The sumscore of the responses to the items is the estimator of the position of the patient on the continuum. The rationale behind this procedure is classical test theory. The main assumption in this theory is that all items are parallel instruments. The Rasch model offers an alternative scaling procedure. With Rasch both respondents and items are scaled on the same continuum. Whereas in Likert scaling all items have the same weight in the summating procedure, in the Rasch model items are differentiated from each other by 'difficulty'. The model holds that the probability of a positive response to an item is dependent on the difference between the difficulty of the item and the value of the person on the latent trait. The rationale behind this procedure is item response theory. In this paper both scaling procedures and their rationales are discussed.

Working Hours, Coping Skills, and Psychological Health in Japanese Daytime Workers

“…Participants were instructed to rate their psychological health during the past month. Although the response categories in the original scale are 0 (rarely), 1 (sometimes), and 3 (often), we revised the categories to 0 (rarely), 1 (sometimes), and 2 (often) because in Likert scaling, every item is generally scored on an ordinal level with equally spaced response categories in order to estimate the participants' positions on the continuum with the sum of the scores of the responses to the items 21) .…”

The Global Usability Score: A Novel Comprehensive Tool for Assessing, Ranking, and Compare Usability of Inhalers in Patients Requiring Airway Treatments

“…Furthermore, the assessment of patients' opinions results partially biased because obtained by means of a Likert scale (ranging 1-6; 1-5 only for the satisfaction domain) which patients were asked to respond after two separate training sessions. The major intrinsic criticism to this questionnaire is that the Likert scaling assumes that distances between each item are equal, such as that all items are valued of the same weight and power in contributing to the four different scores of the questionnaire [26,27].…”

The information content of financial survey response data

“…Assume a survey collects n independent k − point Likert-scale observations for each of the survey questions. Let the Likert scale represent a polytomous Rasch model, with say 5, 7 or 9 divisions (Alphen et al 2008;Bond and Fox 2007;Fitzpatrick et al 2004;White and Velozo 2002;Likert 1974). We can take the perspective of a polytomous Rasch model, assuming that the responses to the survey map an underlying Gaussian ℕ(μ, σ 2 ) belief distribution to a Likert item across the population of subjects surveyed for a particular question on the survey.…”

“…The survey researchers' challenge is to record subject responses in mappings that are balanced, properly scaled, meaningful, informative, accurate and unbiased. There is considerable discussion as to the exact meaning of Likert scaling (Alphen et al 2008;Bond and Fox 2007;Fitzpatrick et al 2004;White and Velozo 2002;Likert 1974). Likert scales are sometimes considered an implementation of a Rasch model, though not every set of Likert scaled items can be used for Rasch measurement, but in practice data has to be thoroughly checked to fulfill the strict formal axioms of the Rasch model (Norquist et al 2004, Bond andFox 2007).…”