In a Nutshell think of it this way…
Psycho (something psychological) + Metric (measurement) = Psychometric (measurement of psychological capabilities)
While it is beyond the scope of this training program to unpack the process whereby psychometric tests are developed, it is important to take note of a few things. Psychometric tests are developed by test developers who are typically research psychologists. These are people who have deep knowledge of a field called research methodology and statistics. In developing tests, they must design them in such a way that they conform to scientific principles such as item validity, predictive validity, content validity, reliability and so on. They also must apply the unreleased test on large numbers of subjects to develop norms and at the end of the day, must ensure that their tests conform to standards set by Assessment Standards South Africa. Test development is a costly, time consuming and rigorous process and it frequently takes years for a test developer to take a test from concept, to approval by the regulating authorities and eventually to market where they can be used by suitably qualified people.