INDEXES VERSUS SCALES

    Both indexes and scales are composite measures--combining more than one indicator of a variable.  Indexes are simpler than scales.  Typically, the indicators combined in an index are given equal weights (though exceptions can be made).  Suppose we ask five questions on a question, each representing prejudice against women.  We could give each person one point for every prejudiced response and add up their number of points.  Some subjects would have few or no points, representing little or no prejudice against women, while others would have lots of points, indicating lots of prejudice.

    Scales differ from indexes by looking for and using any intensity structure that may exist among the indicators being combined.  Subjects are then scored on the basis of their overall pattern of responses.  Possible indicators of prejudice against women might include agreement with the following statements: (1) "Women are weaker than men." (2) "I wouldn't vote for a female candidate for office." (3) "Women should not be allowed to vote."  Opinion (3) clearly represents more prejudice than the other opinions, and (2) represents more prejudice than  (1).  Knowing how many opinions a person held would allow us to accurately predict which they were.

    Scales are constructed in such a way as to take account of such intensity structures.  As you'll see, there are a number of different types of scales available to the social research.