a graphic representation of bivariate (2 variable) data as a set of points in the plane that have Cartesian coordinates equal to corresponding values of the two variates.

a method creating a regression line or estimating values from a set of observations by minimizing the sum of the squares of the differences between the observations and the values to be found.

a variable that is not included as an explanatory or response variable in the analysis but can affect the interpretation of relationships between variables.

is a paradox in probability and statistics, in which a trend appears in different groups of data but disappears or reverses when these groups are combined. It is sometimes given the impersonal title reversal paradox or amalgamation paradox.