Variable is the core concept in empirical research of psychology,which is to explore the factors that can be divided into two types,i.e.existing variable and induced variable.In empirical research of psychology,the basic logical starting point is variable,and the nature of research is the relationship between variables.According to the relationship between variables,psychological empirical research can be divided into two types,i.e.correlation research and causality research;the former is applied to study the relationship between two existing variables and the latter is applied to study the causality between two induced variables.Different types of psychological empirical researchs need to adopt different research designs and statistical methods.