Association between events can be positive or negative. Negative association shows that the more of one event, the less of the other, while positive association shows the more of one event, the more of the other.

To determine if two events are associated, statisticians sometimes use a mathematical technique known as a chi-square test.

Another tool for organizing information or numbers is a matrix. Matrices look like rectangular tables but typically do not use lines to frame each cell.

Information that places something in a given category—such as eye color—is called categorical data. Information that can be ordered on a number line—such as height—is called quantitative data.