Screening questions are placed in the beginning of a survey in order to determine whether the respondent is eligible to take up the survey. Only testers who are eligible as per the pre-set conditions are allowed to proceed to taking the entire test.
For instance: If a study is being done on Chocolates, a relevant question would be
“How often do you eat chocolates?”
Screening questions are very necessary in order to eliminate unwanted respondents and filter our the right candidates. The advantage of doing this is it makes data analysis much better with proper insights.