Behavioral Science, Volume 17, 1972, 490-491.
NSCALE: A program to analyze and score a scale battery
John J. Ray
University of New South Wales
Programs such as that by Kohr (1971) are suitable for obtaining an item analysis for a single existing Likert (or other summafive) scale and programs such as ITRO and ITRA (Ray, 1972) are suitable for producing new scales from a body of trial items. Another application -- one that is often very important in survey research -- is to produce item analyses for a whole battery of scales. It is this latter task for which the present program is designed.
The importance of the application can be seen from the fact that scale reliabilities often vary markedly according to the population used (Ray, 1971) and consequently it is a frequently recommended practice to check the internal consistency reliability of scales on every occasion of their use. In the normal survey where several scales are used this task of checking would be very laborious if each scale had to be processed separately using one of the existing programs mentioned above. With program NSCALE, on the other hand, the data have to be set up and run only once to produce a complete set of item analyses.
The index of scale adequacy used by NSCALE is Cronbach's (1951) coefficient alpha. This is equivalent to the mean of all split-half reliabilities. As a subsidiary index independent of scale length, the estimated mean interitem correlation is also computed for each scale. The index of item adequacy used is the corrected item-total correlation. Unlike the Kohr (1971) program the older "differences between upper and lower thirds" method is not included. As the older method is simply a less precise version of the other, this omission does lead to a more efficient use of memory.
Options are available for rescoring (where the items of several scales occur interspersed among one another) and for reversals (used in balanced attitude scales where "Agree" sometimes earns a high score and sometimes earns a low score).
Information automatically output comprises: total no. of items; total no. of subjects; input parameters; a set of total scores for each subject (put out on both cards and line-printer); means and standard deviations for all items and all totals; item-total correlations; alphas and mean interitem correlations for all scales.
The program is written entirely in FORTRAN IV and requires core storage only.
A program listing and manual are available from the author on request.
Cronbach, L. J. Coefficient alpha and the internal structure of tests. Psychometrika, 1951, 16, 297-334.
Kohr, R. L. An item analysis and scoring program for summated rating scales. Educational & Psychological Measurement, 1971, 31, 769-770.
Ray, J.J. (1971) "A new measure of conservatism" -- Its limitations. British Journal of Social & Clinical Psychology, 10, 79-80.
Ray, J.J. (1972) A new reliability maximization procedure for Likert scales. Australian Psychologist 7, 40-46.
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