statistics

Relationships between variables are often examined in research. When two variables are related such that a change in one is associated with a congruent change in the other, it is called correlation. The direction and degree of correlation between two interval or ratio scale variables (X and Y) are graphically represented on a scatter diagram (1.1) by plotting the corresponding values (1.0). A measure of this relationship, represented by the symbol r, is called a correlation coefficient. (1.2)
(1.0)
X (aptitude test) Y (achievement test)
25 97
54 86
60 100
64 90
24 40
25 87
34 68
56 92
26 ...