The sociologist Paul Millar has created a very useful tool in Stata called optifact for creating summated scales. Often social scientists simply throw together some variables, report a Cronbach's alpha as a measure of reliability, and then move on to other analyses. But there are some well-known problems with Cronbach's alpha; in particular, the value of alpha will increase if you add more items in the scale. Millar's program is useful because for those items which load on one dimension, it sorts candidate scales by increasing number of items in descending order of Cronbach's alpha. For instance, the program will first list all scales with, say, two items that load on one factor, starting with the scale with the highest Cronbach's alpha. This way the analyst can easily create summated scales that are parsimonious (i.e., consist of few items), unidimensional (i.e., load on one factor), and have a high level of reliability (i.e., have a high Cronbach's alpha).
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