Work-related Personality Inventory Manual

1. Introduction

The Work-related Personality Inventory, the WPI, is a personality questionnaire that is developed for the Human Resource Management (HRM) by Ixly[1]. The WPI consists of five factors, subdivided into 25 scales.

First, this manual will focus on the concept of ‘personality’ and the theoretical background of the WPI. Following this, the development, norms, the reliability and validity of the questionnaire will be discussed. Finally, the application of the questionnaire, the interpretation of the results and which conclusions one can draw from the results will be elaborated on.

1.1. Personality

The term personality is based on the Latin word Persona, which means ‘mask’. When we strictly define personality as mask, we could see at as the aspect of ourselves that we show the outside world (Hergenhahn, 1980). Several theorists have focused on the concept of personality. The theory of personality by Freud – with its trichotomy in the ID, the EGO and the Superergo – is probably the best known. The theories by Maslow, Jung and Rogers are quite well known as well. For this, see for example Hergenhahn (1980).

There is a lot of discussion on the exact definition of personality. Because of this, there are a large number of different definitions, ranging from simple versions to complex technical definitions including mathematical equations. A couple of examples:

  • Personality can be describes as ‘a collection of attributes of the way in which situations are distinguished, interpreted and evaluated by a person. This interpretation and evaluation influence the behaviour a person will show in the specific situation’ (Hoekstra, Ormel & Fruyt, 1996).
  • Personality is ‘the content of what is said about someone with the intent to give a specific explanation for his or her behaviour. Including the one who makes the statement about the person in the definition is important because someone’s personality often depends to a large extent on the judging person and the person that is judged him/herself’ (Hofstee, Brokken & Land, 1981).

Nowadays, the most prominent theory in the research on personality is the Five Factor Model (Allport & Odbert, 1936; Cattell, 1943). This theory is also called the Big Five (Goldberg, 1981). The principle of the Five Factor Model is closest to the principle of the WPI.

The Five Factor Model (FFM)
The FFM has its origins in the (psycho)lexical hypotheses. These state that all individual differences between people that matter can be expressed in language. More concrete, this means that trait adjectives from the American dictionary were collected by Allport and Odbert (1936) and later by Cattell (1943), in order to come to a complete as possible reflection of human personality. This collection was found to be describable by a five factor model. This conclusion was based on principle component analysis on the trait adjectives, collected as self-evaluations or evaluations by others. After this a varimax rotation of these components was performed, to obtain positions of the axes for which the components are as easily interpretable as possible. The position of the axes is optimal when the adjectives load highly on one component and show a negligible loading on the other components. The components are then interpreted using the items with the highest loadings.

The theory of the FFM states that there are five main factors or dimensions of personality characteristics on which people differ from each other and can be compared on. The five factors of the FFM are:

  1. Extraversion
  2. Agreeableness
  3. Conscientiousness
  4. Neuroticism
  5. Openness to experience. (Allport & Odbert, 1936; Cattell, 1943)

Development and stability of the personality factors
During adolescence it is possible for the scores of a person on the five factors to change somewhat. Often the scores on Agreeableness and Conscientiousness increase a little, while scores on Extraversion, Neuroticism and Openness to experience decrease somewhat. It appears that from the age of thirty no substantial differences in scores occur. From that moment on, consecutive test scores correlate highly. A person thus has a stable profile from that age on (McCrae & Costa, 1994). McCrae and Costa (1994) found remarkable stability of the factors in longitudinal research. This stability was also found in cross-sectional research. Changes are not impossible, for example when dramatic events occur in a person’s life, but in general we can say that the personality profile of a person is relatively stable.

Gender differences
There are differences in the scores on the FFM between men and women. These differences are found in different cultures. Women on average score higher on the factor Agreeableness (Sociability) and lower on the factor Stability (de Dusschooten, 2004). Women on average score higher on Attentiveness and Need for contact (Beutel & Marini, 1995). Men score higher on Status and Influence (Aries, 1976). Research investigating the association between personality characteristics and educational attainment has also shown that there are differences between men and women. The association between personality and education is higher for mean than for women (van Eijck & de Graaf, 2001).

1.2. Measuring personality in practice

Personality can be measured with a psychological test. This concept can be described as follows:

‘A systematic evaluation- and measuring procedure, which makes it possible to make statements about one or more personality characteristics of the examined person or of his or her future behaviour or future performance’.

These statements are based on an objective and comparative processing of the reactions and performance of the examined person on carefully selected assignments or question, which are presented to his/her in a standardized manner (Drenth, 1981). The reactions of the person form the test information on which the statements are made. This test information can be obtained in several ways, for example by means of self-evaluations, observations, instrumental measurements or objective documentations (Drenth, 1981).

The personality questionnaire is an example of a psychological test. The most important distinction that is made in tested behaviour is the distinction between tests of performance and tests of behaviour or conduct (Drenth & Sijtsma, 2006). A performance test, with right or wrong answers, demands a maximum performance of the examined person. For tests of behaviour there is no pre-determined ‘right/wrong key’ available. Because tests of behaviour are not tests in the sense of ‘aptitude’, we often speak about ‘questionnaire’ in this context (Drenth & Sijtsma, 2006).

Since the twenties of the previous century, personality questionnaires are often used in practice. For a long time, no clear relation was found between criteria of good work behaviour and the outcomes of the questionnaires (Salgado & de Fruyt, 2005). There was a clear distinction between practice and research. Despite this fact personality questionnaires remained popular in practice. In addition to the use in (mental) health care, the so called psycho-diagnostics, they can be used in the field of HRM and personnel selection as well.

Essential for the use of personality questionnaires in the work field of HRM is predictive validity: to what extent does personality have predictive value for (future) job performance? In recent years research has shown that personality questionnaires have predictive value in personnel selection. Several studies have shown the predictive validity of the factors of the FFM. Two of the five factors, Extraversion and Conscientiousness, appear to be particularly good predictors of job performance (Schultz & Schultz, 2002). The predictive value appears to differ between different research populations. Research by Barrick & Mount (1991) on the FFM and job performance shows that Conscientiousness is a good predictor for all examined groups. The same study shows that Extraversion and Agreeableness are predictors for managerial positions only and that Openness to experience is a predictor for trainers. Extraversion mainly appears to have predictive value for performance in occupations in which social interaction and sales are central (Barrick & Mount, 1991). The conclusion by Barrick and Mount is mainly that Conscientiousness would be a good predictor of job performance. Furthermore, they state that the FFM is a good tool to investigate personality in the workplace. The same conclusions are drawn in a smaller study by Tett, Rothstein and Jackson (in: Salgado & de Fruyt, 2005, p.176).

The initiative within Ixly for the development of a personality questionnaire came from the HRM field: there was a need for a personality questionnaire specifically developed for the use within the HRM work field. The personality questionnaires that were used in this field did not meet the needs of the assessment psychologists. The goal of the development of this questionnaire was to form to an as complete as possible questionnaire, covering all the aspects of personality that are relevant for work situations. Furthermore, there was the need to substitute the relatively time intensive questionnaires that were used to get a personality profile with one questionnaire from which a similar personality profile could be distilled but within a shorter time period.

Personality, as it is operationalized in the WPI, can be defined as follows:
‘A reasonably stable behavioural tendency that is most likely to be shown in relevant (work) situations’.

With behaviour, we mean the instrumental actions one takes. Orderliness and Agreeableness are examples of this. Behaviour also encompasses the cognitive actions, sometimes called ‘covert behaviour’. One can think about things like Attentiveness and Originality.

Assessment psychologists indicated that they were in need of ‘narrow’ constructs in personality questionnaires. With narrow constructs we mean psychological constructs that are not indicative of more personality attributes. Psychologists find differentiation very important: they often want as many constructs as possible. However, in academics, more limited and simpler questionnaires are preferred. The WPI is developed for the field of practice, making sure that no relevant differentiations that can be of interest in a work-related personality questionnaire are lost.

[1] Ixly (previously Orga B.V.) is a publisher of online instruments and is dedicated to the development, research and publishing of questionnaires and tests for the HRM profession. These are distributed via an online application.