Control of Error

Psychometric assessments are designed to maximise objectivity by systematically reducing four main sources of error in assessing individual differences. These are:

– Test-related sources: ambiguous items, relevance of items; item complexity

– Candidate-related sources: variations in mood, motivation, health; test sophistication

– Administration: test conditions, test administration,

– Scoring and Interpretation: Limiting bias and subjectivity

From a test design perspective both the number and the quality of items is critical.  The more we increase the number of robust test items, the more certain we can be of assessing someone’s true ability. Each additional item reduces sampling error and increasing the test reliability. Psychometric tests are therefore characterised by relatively large number of short items increasing in difficulty in order to get an accurate measure of an individual’s capability in a particular area. There is however a limit to the number of questions as candidates eventually tire of more questions and the added return in extra reliability must therefore be balanced by the time it takes to collect the information (depth versus breadth).

We must also be proactive to manage candidate factors that can lead to error. In reality, for many people being asked to complete a psychometric test provokes huge anxiety. This anxiety is concerned with both uncertainties about what the assessment might involve and concerns about the potential results of the assessment.  Too often people arrive for a psychometric assessment without even knowing if the assessment will involve abilities, interests or personality. Some people are further disadvantaged by having limited experience of some of these assessment tools.  It is useful to be able to direct a prospective test taker to some practice items relevant to assessments they will be undertaking.  The Career’s Portal for Imperial College, London has excellent links to practice tests where you can experience many common selection tests used by employers. SHL also provide a good range of sample assessments:

Best practice administration underpins the quality of the whole assessment process, by putting systems in place to ensure administrators:

√    Explain why they are using the assessment you are using and it’s purpose

√    Demonstrate familiarity with the items in the assessment and their relevance to the job

√    Gain the informed consent of the candidate

√    Administer the assessment fairly (conditions, time, special needs)

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