You can use the survey question validation to force respondents to answer a question or request that they consider answering the question before leaving the page. These options can also be used to force a certain type of response (e.g., valid phone numbers only).

There are four main validation features available for nearly every question type: Force Response, Request Response, Custom Validation, and Custom Validation Messages. When any of the validation options are enabled, an asterisk icon will appear to the left of the question, indicating that the question has some form of validation.