This document discusses the purpose and design of questionnaires and experiments. Questionnaires can measure factual, behavioral, and attitudinal information through open-ended and closed-ended questions with multi-item scales. The purpose is to elicit information non-evaluatively. Experiments compare results between a treatment group that receives a condition and a control group that does not to measure effects of the treatment. Questionnaires and experiments aim to obtain quantitative and qualitative data through standardized, simple questions and randomized group assignments.