Indices and Scales

1. Indices and Scales

2. 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.

3. 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).

4. 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.

5. 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.

6. 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.

7. 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.