Guttman scale

A Guttman scale is a psychological instrument developed using the scaling technique developed by Louis Guttman in 1944 called Guttman scaling or scalogram analysis. A primary purpose of the Guttman scaling is to ensure that the instrument measures only a single trait (a property called unidimensionality, a single dimension underlies responses to the scale). Guttman's insight was that for unidimensional scales, those who agree with a more extreme test item will also agree with all less extreme items that preceded it. A perfect Guttman scale A hypothetical, perfect Guttman scale consists of a unidimensional set of items that are ranked in order of difficulty from least extreme to most extreme position. For example, a person scoring a "7" on a ten item Guttman scale, will agree with items 1-7 and disagree with items 8,9,10. An important property of Guttman's model is that a person's entire set of responses to all items can be predicted from their cumulative score because the model is deterministic. An important objective in Guttman scaling is to maximize the reproducibility of response patterns from a single score. Another commonly used metric for assessing the quality of a Guttman scale, is Menzel's coefficient of scalability and the coefficient of homogeneity. In order to maximize unidimensionality, misfitting items are re-written or discarded. The Guttman scale is used mostly when researchers want to design short questionnaires with good discriminating ability. The Guttman model works best for constructs that are hierarchical and highly structured such as social distance, organizational hierarchies, and evolutionary stages. In many ways, Guttman's deterministic model is complemented by probabilistic item response theory models, especially Rasch measurement. However, IRT analysis requires considerably longer instruments and large datasets. A class of unidimensional models that contrast with Guttman's model are unfolding models. These models also assume unidimensionality but posit that the probability of endorsing an item is proportional to the distance between the items standing on the unidimensional trait and the standing of the respondent. An example of a Guttman scale - the Bogardus Social Distance Scale: (Least extreme) 1. Are you willing to permit immigrants to live in your country? 2. Are you willing to permit immigrants to live in your community? 3. Are you willing to permit immigrants to live in your neighborhood? 4. Are you willing to permit immigrants to live next door to you? 5. Would you permit your child to marry an immigrant? (Most extreme) E.g., agreement with item 3 implies agreement with items 1 and 2. The Guttman’s scale is a species of thermometer that integrates a list of such postpositions that adherence to a higher level, necessarily implies adherence to the lower levels. It serves to discover the attitudes of the individual hierarchy, determining your level of commitment and adherence. Applied individually and collectively. An atmosphere of trust should foster so that respondents answer without inhibitions. To build it there must be seek different sets of actions, situations and elements in relation to a reference. Play with these three sets of issues (actions, situations and elements) to configure different alternatives. Analyze the options arising from previous handling. Rank the statements with the help of a group of experts with specific procedures identified by Guttman, to at the top of the scale are located which indicate an attitude more radical and at the bottom of less committed attitude.