An experiment designed such that neither the participants nor the researchers observing them know which participants are in the experimental and control groups until after the observations are complete. Double-blind experiments are particularly important in the field of medicine because they control for both the placebo effect and unconscious bias on the part of the researchers — two factors that can make the results of a medical study difficult to interpret. To learn more, visit our side trip Fair tests in the field of medicine.

Information gleaned from observations — usually observations that are made in a standardized way. The term data generally refers to raw data — information that has not yet been analyzed. Data (multiple pieces of information) is the plural form of datum (a single piece of information).

To figure out through logical reasoning. Deductions are often based on established knowledge and/or assumptions.