How Valid Are Personality Tests?

Personality testing is a multi-million dollar industry. There are thousands of psychometric tests on the market. Some of these are for personal entertainment, other tests are designed to test applicants for particular occupations or aptitude.

With so much weight often put on these tests, how valid are psychometric tests and what are their flaws?

Psychometric Tests - Their Reliability and Validity

Reliability stats of psychometric tests will show how much, on average, the results tend to change if the same person completes the same questionnaire a second time. Validity stats refer to what the test score actually measures. Some researchers, for example, question whether IQ tests are accurate indicators of intelligence. Or could it be these tests are simply a measure of how one person's IQ scores compare with another person's score on IQ tests?

Personality Test Disadvantages

One disadvantage of psychometric tests is that they can give a static and mechanical view: they give the impression that say, an IQ score or personality profile is fixed and this in turn, could bring about its permanence. Tests claim to be scientific and objective and some people are ready to believe the results emphatically. Rather like intelligence,personality is another difficult concept to define and different theories of personality favour different approaches to measurement and assessment of personality.

Psychometric Assessments - What they Measure

Personality tests can measure a number of characteristics such as: needs, traits, motives, values and behaviour. But when all is said and done, a test that adequately measures a particular concept will have that concept in common, no matter what the test title.

To be useful, tests must relate to some criteria exterior to itself. This is perhaps the biggest issue with respect to psychometric tests. Binet for instance, established that scores on his test differentiated between children thought to be bright or dull, based on school performance.

Predictive validity also asks whether the measure of a test can be compared with some future criterion. Richardson in the early 1990's asked whether this correlation with school performance makes IQ tests valid tests of educational prediction rather than valid tests of intelligence.

IQ Tests and Their Accuracy

The teacher might also ask, for all the time and money that have been spent on intelligence tests, whether they're really of much value within the educational context. But in this, it has actually been found that IQ tests do actually remain one of the most accurate predictors of educational achievement. Test scores have a strong correlation with a child's present and future levels of academic success.

It is also important that the scores on say, one intelligence test relates to scores on another intelligence test and this is referred to as concurrent validity. If they don't, then not only might the test be measuring nothing at all, but it begs the question: what is intelligence if two intelligence tests are supposed to be measuring the same thing?
Aptitude Test and their Validity

Equally, ecological validity asks how the results of a test compare with its equivalent in the real world. Content-related validation is of great importance to personnel selection tests, for in order to be effective, a job analysis must be specific.

Some tests use "simulators" to reproduce the functions performed in the job. Simulators, for instance, have been used for both training and testing purposes in the NASA space program.

Finally, face validity (sometimes called "surface validity") basically asks whether the test looks as if it is measuring what it is supposed to. Does the test, on first acquaintance, seem reasonable to the person taking it? This is an important question for if items of the test do not seem valid then either the whole process won't be taken seriously, or there may be some valid objections to the test.

Validity studies do, however, have their limitations, including sampling error. Also some validity studies tests a fairly small sample. Lack of face validity can have a very negative impact on test procedure.

Sources:

• Annastasi A. Psychological Testing. Sixth Edition Macmillan Publishing Co., London. 1988.
  
• Cronback, L. Essentials of Psychological Testing. Harper International Edition, New York and London. 1970.
  
• Edenborough R. Using Psychometrics. Kogan Page Ltd, London. 1974.
  
• Hayes, N. Foundations of Psychology. Routledge, London. 1994.
  
• Helmstadter G. Principles of Psychological Measurement. Methuen & Co. London. 1996.