The variables obtained when two aspects of the same phenomenon are simultaneously observed are called two-dimensional statistical variables. They are represented by the pair (x,y), which takes the values (x₁,y₁), (x₂,y₂),..., (x_n,y_n).

The distributions where those variables determine are called two-dimensional distributions.

(1)   Arithmetic mean

(2)   Covariance

(3)   Standard deviation

(4)   Variance

(5)   Pearson product-moment correlation

(6)   Regression line

(7)   Result interpretation