The use of examinations to separate qualified from unqualified individuals dates back to at least 2200 BC, when Chinese civil servants were required to demonstrate their fitness for various jobs (Gregory 2004). The use of tests to certify competence continues today for teachers, lawyers, crane operators, and those employed in hundreds of other occupations. According to the Bureau of Labor Statistics and other estimates, nearly 30 per cent of the workforce is licensed or certified, and of those who are, more than 90 per cent were required to pass a test (Gittleman et al. 2017). Given that credentialling tests have an impact on the lives of hundreds of thousands of individuals each year, it is essential that their scores should be valid for this purpose. 1

This entry presents an overview of the development and use of tests for making decisions about whether individuals possess the knowledge and skills required to work in an occupation or profession. Credentialling tests are expected to adhere to the same principles that guide test use in educational and employment settings. Almost all credentialling tests consist of multiple-choice questions or some other written format, typically administered by computer at a location dedicated to test administration. However, given that scores on credentialling tests sometimes support claims about on-the-job skills, credentialling programmes also make use of various types of performance assessments. Indeed, some credentialling programmes have made notable contributions to the field of measurement through the development of performance tests, computerised simulations, and automated scoring procedures, as well as through the use of psychometric models required to score these complex assessments. Given their high stakes, credentialling tests are subject to the same risks and legal challenges faced by employment tests. Credentialling programmes, probably more so than other types of tests, are often the target of organised efforts to pirate test items and other intellectual property. The following text describes the development and use of credentialling tests, focusing on those features that distinguish them from educational achievement and employment tests.