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Chapter 6. Indexes, Scales, and Typologies. Index and Scale. Index Constructed by accumulating scores assigned to individual attributes. Scale
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Chapter 6 Indexes, Scales, and Typologies
Index and Scale • Index • Constructed by accumulating scores assigned to individual attributes. • Scale • Constructed by assigning scores to patterns of responses, recognizing that some items reflect a weak degree of the variable while others reflect something stronger.
Index and Scale: Similarities • Both are ordinal measures of variables. • Both rank order units of analysis in terms of specific variables. • Both are measurements based on more than one data item.
Index and Scale:Scoring Differences • Index • Accumulate scores assigned to individual attributes. • Scale • Assign scores to patterns of responses.
Index-Construction Logic • Below are political actions with similar degrees of activism. To create an index we might give people 1 point for each of the actions they’ve taken.
Scale-Construction Logic • Below are political actions with different degrees of activism. To construct a scale we might score people according to which of the ideal patterns most closely describes them.
Constructing an Index • Select items for a composite index. • Examine empirical relationships. • Assign scores for responses. • Handle missing data. • Validate the index.
Selecting Items Criteria • Face (logical) validity • Unidimensionality • General or specific • Variance
Hypothetical Trivariate Relationship Among Scientific Orientation Items
Empirical Relationships • Established when respondents’ answers to one question help predict how they will answer other questions. • If two items are empirically related, we can argue that each reflects the same variable, and both can be included in the same index.
Assign Scores for Responses Two basic decisions: • Decide the desirable range of the index scores. • Decide whether to give each item in the index equal weight or different weights.
Ways to Handle Missing Data • Exclude cases with missing data from the construction of the index and the analysis. • Treat missing data as one of the available responses. • Analyze missing data to interpret the meaning.
Validate the Index • Item Analysis - internal validation. • External validation - ranking of groups on the index should predict the ranking of groups in answering similar or related questions.
Techniques of Scale Construction • Bogardus social distance scale - measures the willingness of people to participate in social relations. • Thurstone scales - judges determine the intensity of different indicators.
Techniques of Scale Construction • Likert scaling - uses standardized response categories. • Semantic differential -asks respondents to rank answers between two extremes. • Guttman scaling - uses an empirical intensity structure (most common).
Semantic Differential: Feelings about Musical Selections • The semantic differential asks respondents to describe something or someone in terms of opposing adjectives.
Typologies • The classification (typically nominal) of observations in terms of their attributes on two or more variables. • The classification of newspapers as liberal-urban, liberal-rural, conservative-urban, or conservative-rural would be an example.
