With Feedbackly, you can set the probability that a question will be shown to a respondent within your survey. This means that if you create a question and set the probability to 50%, there is a 50% chance that the question will be included in your survey to a given respondent.
This is useful if you have a high number of questions and need a representative sample for each one, instead of showing a very long survey, you can get a sample of responses on certain questions.
To do this: In the survey creator, click the 'advanced settings' option at the top of the question window. Then simply drag the probability slider in the upper left side of the question window. Note that the probability can be changed for each question (with a default probability of 100%).