Locus of control
Measuring scales

The Duttweiler (1984) Internal Control Index (ICI) addresses perceived problems with the Rotter scales, including their forced-choice format, susceptibility to social desirability and heterogeneity (as indicated by factor analysis). She also notes that, while other scales existed in 1984 to measure locus of control, "they appear to be subject to many of the same problems". Unlike the forced-choice format used on Rotter's scale, Duttweiler's 28-item ICI uses a Likert-type scale in which people must state whether they would rarely, occasionally, sometimes, frequently or usually behave as specified in each of 28 statements. The ICI assess variables pertinent to internal locus: cognitive processing, autonomy, resistance to social influence, self-confidence and delay of gratification. A small (133 student-subject) validation study indicated that the scale had good internal consistency reliability (a Cronbach's alpha of 0.85).
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