Learn in the textbookStatistical Analysis and Inference
DefinitionThe correlation coefficient (相関係数) is an index that expresses, as a number from −1 to +1, which way and how strongly two variables move together in a linear relationship.
ExplanationA positive value means positive correlation, where one variable tends to rise as the other rises, and a negative value means negative correlation, where one tends to fall as the other rises; the sign shows the direction, and the size of the absolute value shows the strength. A scatter plot (散布図) places each pair of values as a dot on a plane with a vertical and a horizontal axis, and the closer the absolute value is to 1, the more closely the dots line up along a straight line.
Memory hookIt is often written with the symbol r.