Practice Guide to Testing in English as a Foreign Language
When testing candidates for whom English is a second or additional language, it is better for candidates to complete the tests in their native or primary language. This allows you to separate the measurement of the skill of the test, e.g. verbal reasoning, from the knowledge of language. There are a few circumstances where it may be appropriate to test a candidate in another language – see below.
Even if people are quite proficient in another language (English), their reading speed may be slower than in their primary language – particularly if a different script is involved. This can create a disadvantage with strictly timed ability tests. Misunderstanding of a single word can prevent a candidate answering a whole question. In numerical reasoning, language can be an issue where questions are expressed in words. Even fluent speakers may not know the meaning of words expressing mathematical functions, e.g. x as a percentage of y may be misunderstood to mean y as a percentage of x.
Personality and other questionnaires do not have time limits and often use quite straightforward language. However, subtle differences in understanding of questions can lead to a greater error of measurement. It is therefore better to complete these questionnaires in the primary language if possible.