Indices and Scales

Indices Use sets of responses to questions to provide measures of underlying constructs Each question that makes up an index constitutes an individual indicator for that construct One analogy for an index is a test, and approaches to index validation work for test- item validation as well.

Scales SCALING creates a measure of a variable expressed as a numerical score. This measure can be any of the following: ordinal (ranked, as with opinion measures), interval (ranked with known distances between rankings, as with “degrees” of liking or disliking something), or ratio (interval with known proportions among scores due to existence of a “true zero,” as with age and income).

Likert Scales Likert scales provide ordinal-level measures of attitudes. Likert scales always run from one extreme evaluative response to another. Likert scales are generally combined to formulate a composite index of some underlying construct. This is why “additive scaling” is typically Likert scaling. Likert scales are simple to produce and answer and aid in comprehensive indicator measurement. The greatest problem with Likert scales is a form of bias known as response set. Another problem is that equivalent scores don’t necessarily mean equivalent responses.

Bogardus Social Distance Scales Bogardus scales measure liking or antipathy between social groups. Groups that dislike one another have greater “social distance” separating them. The scale proposes a number of hypothetical situations of social interaction. Social distance scales are used to measure overt and symbolic racism and various anti-outgroup sentiments, although their findings are always questionable if not presented comparatively and in context.

Semantic Differential Scales These are indirect measure of how a person feels about a concept, object or other person. Adjectives express opposite forms of evaluation (good vs bad), potency (strong vs weak) and activity (active vs passive). On response forms, the adjectives are spaced with seven to eleven choices between them, and respondents select one “feeling” per pair. Results expose a more complicated set of attitudes than can be acquired asking straightforward questions.

Guttman, or Cumulative, Scales Guttman scales describe underlying dimensions in survey data. Guttman scales measure the intensity of a concept. Process begins with surveys that ask simple yes-no or present-absent questions about the topic of interest. The researcher determines how many people answered the questions in every possible order, and has a hypothesised order based on question “seriousness.” If the questions all (or predominately) follow the hypothesised logical order, the question set is considered a “true Guttman scale” and can subsequently be used to measure the intensity of underlying constructs in other studies.