Research factors are a very important element in any research design. Research factors include experimental and non-experimental factors. The former is the general term used to describe the similar experimental conditions that researchers are interested in, while the latter are other factors that researchers have little interest in but may influence the result. This article mainly focuses on the following issues: the definition of research factors, the selection and arrangement of experimental factors and non-experimental factors, the interaction between research factors, the standardization of research factors and the common mistakes frequently made by researchers.

Key words: statistics, medical, research design, research factors