Psychometric Tests > Aptitude & Ability Tests - Speed versus Power

Aptitude and ability tests are classified as maximum performance tests as they test what you can achieve when you are making maximum effort. The types of question you can expect will depend on which aptitudes and abilities are needed in the job you are applying for. There are two different styles of maximum performance test.

In a speed test the scope of the questions is limited and the methods you need to use to answer them is clear from the form of the question. Taken individually, the questions appear relatively straightforward. These tests are concerned with how many questions you can answer correctly in the allotted time. A power test on the other hand will present a smaller number of more complex questions. The methods you need to use to answer these questions are not obvious, and working out how to answer the question is the difficult part. Once you have determined this, arriving at the correct answer is usually relatively straightforward.

These speed and power definitions apply only to maximum performance tests like aptitude and ability tests and not to personality questionnaires. In general, if you do well in speed tests then you will do well in power tests as well.

How Your Aptitude Test Results are Interpreted
There are two distinct methods that employers use to interpret your scores.

In criterion-referenced tests, your test score is not compared to that of other candidates but relates solely to your degree of competence in the specific area assessed. This type of assessment is generally associated with achievement testing and certification.

In norm-referenced test interpretation, your scores are compared with an appropriate norm group. This is done by comparing the educational level, occupation, language cultural background and other demographic characteristics of the individuals making up the test group and the norm group to ensure their similarity.

Whenever you take a psychometric test either as part of the selection process or as a practice exercise you will usually see your results presented in terms of numerical scores.

These may be; raw scores, standard scores, percentile scores, Z-scores, T-scores or stens and in order to interpret your scores properly, you need to understand what these mean and how they are derived.

The most important concept to grasp is that of the percentile score. This is the score most often used by organizations when comparing your score with that of other candidates. It has the advantage of being easily understood and percentiles are very widely used when reporting results to managers.

To calculate your percentile score, your raw score is converted to a number indicating the percentage of the test group who scored below you. For example, a score at the 60th percentile means that your score is the same as or higher than the scores of 60% of those who took the test.

Aptitude tests have relatively few questions and the people sitting a particular test tend to be from a similar group in terms of their education and background. As a result, the scores tend to cluster quite tightly around the average. This combination of few questions, clustering and the use of percentiles has important implications for you as a job candidate. A small improvement in your actual score will result in a big improvement to your percentile score.

To illustrate this point, consider a typical aptitude test consisting of 50 questions. Most of the candidates, who are a fairly similar group in terms of their educational background and achievements, will score around 40. Some will score a few less and some a few more. It is very unlikely that any of them will score less than 35 or more than 45.

Looking at these results in terms of percentiles is a very poor way of analyzing them and no experienced statistician would ever use percentiles on this type of data. However, nine times out of ten this is exactly what happens to these test results and a difference of three or four extra marks can take you from the 30th to the 70th percentile. This is why preparing for these tests is so worthwhile as even small improvements in your results can make you appear a far superior candidate.

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