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How Reliable is PRISM?

To be truly effective, a psychometric instrument should:

   Be reliable

   Be easy to use

   Be easy to administer

Provide an output that is easy to understand one way to think of reliability is that, all things being equal, a person should get the same results on a questionnaire if they complete it at two different points in time. Another way to look at reliability is to say that two people who are the same in terms of the traits being measured, should get the same score.

A three-year study of PRISM by the University of Kent showed that the instrument achieved the following Alpha scores:

Cronbach's Alpha is one of the most common measures of scale reliability in psychometrics and it is generally recognised that an Alpha score of 0.7 or above is an acceptable value of internal consistency in a test  instrument.