1. Questionnaires are a technique for obtaining information from subjects through a series of questions. They can provide statistically useful data on a given topic in a relatively economical way by asking the same questions to all subjects and ensuring anonymity. 2. Properly designed questionnaires should be straightforward, clear, and limited in scope. Questions should determine the type of information needed, limit responses, and be distributed appropriately. 3. Questionnaires can contain closed-ended, open-ended, contingency, or matrix questions. Closed-ended questions limit responses while open-ended questions allow free responses.