If you are running a survey that is similar or the same as a survey that you've run recently, you might want to ensure that you are sending your survey to a completely new sample each time, excluding those who have already taken a previous survey. 

If you are running multiple surveys with different creative assets, you can also use the exclude respondents feature to reduce bias in your A/B tests, by ensuring respondents only see one of your surveys.

We do not recommend excluding respondents from surveys that ran six or more months ago, as it would considerably decrease your available sample. 

When you've drafted your survey and you are moving on the Audience page, you'll see the option to Exclude respondents.

When you click on Exclude respondents, you will have the option to select one or more surveys. Selecting a survey (or multiple surveys) will exclude those respondents from answering the survey you’re drafting. Select the previous (open, scheduled or closed) surveys you wish to exclude. You cannot select to exclude draft surveys, as they don’t have respondents.

You can use the search bar to find surveys by external or internal title. 

Check the Selected tab to see the surveys you’ve chosen to exclude. Click Save Exclusions and continue to complete your draft survey.