Scales to measure locus of control
The most famous questionnaire to measure locus of control is the 13-item forced choice scale of Rotter, the Rotter Internal External Locus of Control Scale (1966), but this is not the only questionnaire - indeed, predating Rotter's work by five years is Bialer's (1961) 23-item scale for children. Also of relevance to locus of control scale are the Crandall Intellectual Ascription of Responsibility Scale (Crandall, 1965), and the Nowicki-Strickland Scale. One of the earliest psychometric scales to assess locus of control, using a Likert-type scale in contrast to the forced-choice alternative measure in Rotter's scale, was that devised by W.H. James, for his unpublished doctoral dissertation, supervised by Rotter at Ohio State University, although this remained an unpublished scale. Many measures of locus of control have appeared since Rotter's scale, both those, such as The Duttweiler Control Index (Duttweiler, 1984), which uses a five-point scale, and those related to specific areas, such as health. These scales are reviewed by Furnham and Steele(1993), and include those related to health psychology, industrial and organizational psychology and those specifically for children, such as the Stanford Preschool Internal-External Control Index,, which is used for three to six year olds. Furnham and Steele (1993) cite data that suggest that the most reliable and valid of the questionnaires for adults is the Duttweiler scale. For a review of the health questionnaires cited by these authors, see below under "Applications".
The Internal Control Index of Duttweiler
A scale with reasonably good psychometric properties has been the Internal Control Index (ICI) of Duttweiler (1984). In her paper on this scale, Duttweiler notes many problems with Rotter's I-E Scale, including problems with its forced choice format, its susceptibility to social desirability and her observation that studies that subject the scale to factor analysis suggest it is not assessing an entirely homogeneous concept. 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" (Duttweiler, 1984, p211). She developed the ICI to assess several variables especially pertinent to internal locus - cognitive processing, autonomy, resistance to social influence, self-confidence and delay of gratification. After administration of this scale to 133 students at Gainesville Junior College in Georgia, United States, she found the scale to have good internal reliability, with a Cronbach's alpha of .85. Unlike the forced-choice format used on Rotter's scale, Duttweiler's 28-item ICI uses a Likert-type scale, in which people have to state whether they would rarely, occasionally, sometimes, frequently or usually behave as specified by each of 28 statements.