Setting question probability
You can set the probability that a particular question in your survey will be shown to a respondent. This means that when you create a question, you can set the probability between 0-100%. If you, for example, select probability of 50%, there is a 50% chance of that particular question being shown to a given respondent. In short, 50% of respondents will see the question, and 50% will not.
Note: if you find that the survey skips some or all questions then most likely the " % of respondents will see this question" is set to zero % or very low. Simply increase the % to show the survey to more respondents.
This is useful if you have a large amount of questions and need a representative sample for each one, instead of showing a long survey, you can get a sample of responses on certain questions.
To do this: In the survey creator, simply drag the probability slider as you like. Note that the probability can be changed for each question (with a default probability of 100%).