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Scales and Indices
Scales and Indices combine several categories in a question or several questions into a “composite measure” that represents a larger concept
Uses questionnaire materials efficiently Why used?
Why Composite Measures
Cannot arrive at a single question that has closed ended answers that adequately describes a concept
Example—religion may have many aspects such as church attendance, belief in God, etc.
May want to analyze several dichotomous variables together, efficiently
Indices and Scales
Both are measures that have “rank order” Both are composites of questions or other
variables
How do they differ?
An index is constructed as a simple sum of effects or values through accumulation of scores or numbers. It is a sum of concepts.
A scale is constructed by assigning scores to a range of intensities of response. Is a measure of intensity of a single concept.
Logic of Construction
See page 150 of the text Index—each respondent type is assigned a
score based on the attribute to be scored, these are summed and a value (a number) is assigned and analysis is done on the number not the respondent type
Scale—the responses are arrayed in order of intensity of some attribute and the intensity measure (a number) is used in analysis
Index Construction
Select the items to be indexed Assign a value to each, can be weighted but
need contributory factor analysis to do this Add the number of responses with a value for
each respondent and construct an index value for the respondent
Must have face validity Unidimensional (unlike scales) Variance
Index Construction
Bivariate relationship—should be related statistically significantly related, this is a crosstab and significance testing issue
Must add something to the concept or the explanation of the concept indexed
Missing data eliminated before the index formed Must have Item validation and index validation—do
the measure and it’s components measure what they purport to and are they sufficient measures
Likert Scales
Really indices No equal measure between levels Likely, less likely, not likely format Assigned values to each level of the “scale”
and you have an equivalent to an index
Scale Construction
Ordinal ranking by intensity of a single variable
Equal importance to each rank in the scale thus a measure of intensity of the concept or the variable used to represent it
Examples—intensity of belief or attitude rather than likely/less likely format
Thurstone Scales
Measure using equal intervals Assigns scores to the intensity of a specific
concept Example 1 to 10—how happy are you right
now (0?) How prejudiced are you? Scales can have zero and negative values,
indices cannot
Guttman Scales
A type of composite measure used to summarize Several discrete and quantifiable observations and to represent some more general variable or concept
Example—scientific orientation would combine 4 questions about specific intensity attitutes and sum then for a scale of scientific orientation
Typology
Multi-dimensional arrays of attitudes or opinions
Usually independent variables arranged in a grid fashion that were originally dichotomous in nature
Uses of Scales and Indices
Example—concept of women’s empowerment
Multiple questions are involved which each discuss an aspect of women’s power to act and decide for themselves
The importance of each must first be evaluated to give a power or intensity to each
They are added and a scale (or if not intensified, an index) is born
Uses
Makes concepts out of groups of attributes or opinions, actions
Gives intensity and scalability