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The Psychometrics Centre

Cambridge Judge Business School

The Psychometrics Centre is working with Thomas International on the development of the Personal Profile Analysis (PPA), their popular, quick and easy to use ipsative personality assessment. The PPA derives its rationale from the 1928 theory of William Marston, who argued that human behaviour was measurable along just two dimensions, which he described as 'external' and 'internal'.  The dimensions interact (High/High, High/Low, Low/High and Low/Low) to produce four modes of expression: Dominance, Inducement, Submission and Compliance (DISC). While we are all able to express any of these modes from time to time, as we mature some become more typical of our behaviour than do others. 

Fifty years ago, Thomas Hendrickson designed an assessment for the four types, which evolved into the Thomas Personal Profile Analysis for the workplace.  The test itself has evolved considerably, so that today it is one of the most widely-used personality assessments world-wide. The PPA has not been without its controversies. For example, it uses an ipsative methodology (comparing good with good and bad with bad) in order to reduce impression management. However, today most of the problems with ipsative scoring have now been resolved and the technique is becoming increasingly popular among other test publishers.

While the words chosen in Hendrickson’s first experiments were based on Marston’s definitive work, subsequent translation and back-translation into more than 24 languages has generated a pool of synonyms that enable us to utilise current advances in test equating and differential item functioning with ipsative data. The result will be translated versions that are able to retain parallelism of the assessment across languages and cultures, an outcome that continues to remain elusive among modern test publishers.

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