When you develop a questionnaire for survey, the questionnaire is distributed to a small set of population (sample) before sending it to the entire population. This is known as pre-test.
Pre-test of questionnaires plays a vital role in reducing the errors that may occur during survey. Pre-tests help researchers identify the problem areas in questionnaire that need fixing before the survey is scaled to bigger population. Conducting pre-test also make sure companies don’t have to spend on rectifying the errors after the survey is scaled to population.