Chapter 2

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"A measure should have validity, describing what it is intended to measure and accurately reflecting the concept."
"It should also have reliability, being consistent in the sense that a subject will give the same response when asked again."
"Statistical methods help us determine the factors that explain variability among subjects.
Variable (VAR) - any characteristic we can measure for each subject, that can vary in value among subjects in a SAM or POP.
Measurement scale - the values the VAR can take


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Classification of VAR
-- whether the measurement scale consists of categories or numbers
-- number of levels in that scale


Quantitative (QUAN) VAR - measurement scale has numerical values
-- values represent different magnitudes of the VAR


Categorical (CAT) VAR - measurement scale is a set of categories
-- distinct categories differ in quality, not in numerical magnitude
-- often called Qualitative (QUAL)




Interval (INT) - the possible numerical values for a QUAN VAR
-- specific numerical distance between each pair of levels


CAT VAR -- unordered and ordered
Nominal scale - CAT VAR for which scale does not have a high or low end, no level is greater than or smaller than any other level, unlike values for QUAN VAR.


Ordinal (ORD) scale - CAT scales that have a natural ordering of values


"A third type of scale falls, in a sense, between nominal and interval.  It consists of categorical scales having a natural ordering of values.  The levels form an ordinal scale.  Examples are social class (upper, middle, lower), political philosophy (very liberal, slightly liberal, moderate, slightly conservative, very conservative) [...]."


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"The scales refer to the actual measurement and not to the phenomena themselves."