Social Research Methods: Qualitative and Quantitative Approaches

QUALITATIVE AND QUANTITATIVE MEASUREMENT

construct in one situation might indicate one part of
a different, complex construct in another situation.
We can combine multiple simple, concrete con-
structs into a complex, more abstract construct. The
principle of unidimensionality in measurement
means that for us to measure a construct, we must
conceptualize it as one coherent, integrated core
idea for its level of abstraction. This shows the way
that the processes of conceptualization and mea-
surement are tightly interwoven.
Here is a specific example. A person’s attitude
about gender equality with regard to getting equal
pay for work is a simpler, more specific and less ab-
stract idea than gender ideology (i.e., a general set
of beliefs about gender relations in all areas of life).
We might measure attitude regarding equal pay as
a unidimensional construct in its own or as a less
abstract subpart of the complex, broader construct
of gender ideology. This does not mean that gender
ideology ceases to be unidimensional. It is a com-
plex idea with several parts but can be unidimen-
sional at a more abstract level.

SCALES AND INDEXES

In this section, we look at scales and indexes, spe-
cialized measures from among the hundreds created
by researchers.^16 We have scales and indexes to
measure many things: the degree of formalization in
bureaucratic organizations, the prestige of occupa-
tions, the adjustment of people to a marriage, the
intensity of group interaction, the level of social ac-
tivity in a community, the degree to which a state’s
sexual assault laws reflect feminist values, and the
level of socioeconomic development of a nation. We
will examine principles of measurement, consider
principles of index and scale construction, and then
explore a few major types of index and scale.
You might find the terms indexand scalecon-
fusing because people use them interchangeably.
One researcher’s scale is another’s index. Both pro-
duce ordinal- or interval-level measures. To add to
the confusion, we can combine scale and index tech-
niques into a single measure. Nonetheless, scales
and indexes are very valuable. They give us more
information about a variable and expand the qual-
ity of measurement (i.e., increase reliability and

validity) over using a simple, single indictor mea-

sure. Scales and indexes also aid in data reduction

by condensing and simplifying information (see

Expansion Box 3, Scales and Indexes: Are They

Different?).

Index Construction

You hear about indexes all the time. For example,

U.S. newspapers report the Federal Bureau of In-

vestigation (FBI) crime index and the consumer

price index (CPI). The FBI index is the sum of

police reports on seven so-called index crimes

(criminal homicide, aggravated assault, forcible

rape, robbery, burglary, larceny of $50 or more, and

auto theft). The index began as part of the Uniform

Crime Report in 1930 (see Rosen, 1995). The CPI,

which is a measure of inflation, is created by total-

ing the cost of buying a list of goods and services

(e.g., food, rent, and utilities) and comparing the

EXPANSION BOX 3

Scales and Indexes: Are They Different?

For most purposes, researchers can treat scales and

indexes as being interchangeable. Social researchers

do not use a consistent nomenclature to distinguish

between them.

A scaleis a measure in which a researcher cap-

tures the intensity, direction, level, or potency of a

variable construct and arranges responses or obser-

vations on a continuum. A scale can use a single in-

dicator or multiple indicators. Most are at the ordinal

level of measurement.

An indexis a measure in which a researcher adds

or combines several distinct indicators of a construct

into a single score. This composite score is often a

simple sum of the multiple indicators. It is used for

content and convergent validity. Indexes are often

measured at the interval or ratio level.

Researchers sometimes combine the features of

scales and indexes in a single measure. This is com-

mon when a researcher has several indicators that

are scales (i.e., that measure intensity or direction).

He or she then adds these indicators together to yield

a single score, thereby creating an index.