Behavioral & Personality Assessment Validity, Reliability & Utility

Thomas PPA - Validity & Consistency

It is generally accepted that efficacy of tests, including behavioral and personality assessments, is best measured by studying three factors: reliability, validity and utility.

Reliability of the Thomas PPA

A test is said to be reliable if it provides the same score for each candidate on different occasions. Thomas International recommends that Thomas PPA be given at intervals of no less than 3 months.

The minimum satisfying figure for test reliability is 0.7 (Kline). The Thomas PPA consistently shows high test/retest reliability. UK data is reviewed regularly.

Predictive Validity of the Thomas PPA

Early data suggested that the Thomas PPA DISC factors achieved predictive validities of up to 0.56 when employees who had been selected for employment using the PPA were rated on their job performance (Thomas Technical Resource Book 2003 TIRR-6, pages 69-70, table 6.3).

Other research by Professor Sidney Irvine focused on particular job roles for specific clients and the results were published in the journal “Current Psychology” (Irvine, Mettam & Syrad, 1994). The research shows that the Thomas PPA gives good predictive validity when objective and verifiable criteria are used. It shows clearly distinguishable profiles for different job types and also differences within profiles for successes and failures in these jobs.


	Construct Validity of the Thomas PPA Any test or behavioral assessment can be said to be valid if it measures what it claims to measure. Construct Validity is where test and retest trials using other instruments are conducted to confirm that the Thomas PPA is saying similar things about the same people. Studies conducted in the UK compare PPA with 16PF and OPQ factor 3 indicate this is the case. Between 1981 and 1987 major trials by suitably qualified practitioners were conducted and these studies clearly show that the Thomas PPA dimensions of Dominance, Influence, Steadiness and Compliance are clearly recognisable when defined by the factor names of these instruments (Thomas Technical Manual 1986).


	Utility & Acceptability of the Thomas PPA Perhaps the most important question to be addressed is: “Is the Thomas PPA questionnaire really useful in the context of recruiting, developing and ultimately retaining talent?” The PPA system is used daily in 60 countries and the feedback confirms that empirically the Thomas PPA has a utility value that is extremely high. The essential purpose of the Thomas PPA and Thomas HJA is to be a structured guide to the interview – for whatever purpose – and bring to mind relevant and incisive questions that focus on the behavioral demands of the job role. Inferences made from information provided in the Thomas PPA’s extensive report set are derived from decades of clinical observations in the workplace. The reports offer to managers and personnel officers a valid personal workstyle frame of reference for each individual candidate. When used correctly, these inferences control for biases and unwanted side effects of unstructured traditional employment interviews.