Trigger conditions specify when to send a particular survey and the persons to send it to. Survey administrators can use trigger conditions to configure the system to generate a survey instance each time a specified action occurs on a specified table, in this example, when an incident closes, the system sends the survey to users that are related to the triggering record, incident callers. You can choose to send a survey every time the condition is met, or you can set a probability for the system to send a survey at random when the condition is met.

in the above trigger condition, the survey will be sent for a caller randomly until 10% of the call is reached when the state is resolved!