A loop is a sequence of instructions that are repeated until a specified condition is achieved. For example:
- A survey may contain a question that asks How satisfied were you with your trip to INSERT RETAILER?, and this question may be repeated once for each retailer that the respondent had indicated they had visited in the previous month (see example below).
- In a computer program may loop through the list of all people in a database, sending an email to each.
Example in survey research
It is a set of questions which are asked more than once where some aspect of each question is varied. For example:
Q10. Which of these brands have you purchased in the last week? Tick all that apply.  Coke  Pepsi  Fanta  None of these LOOP OVER Q11 AND Q12 FOR ALL BRANDS SELECTED IN Q10 Q11. Where were you when you last purchased INSERT BRAND FROM Q10? Q12. Who were you with when you last purchased INSERT BRAND FROM Q11?