The first approach known as “cell occupancy” sets up a 2 by 2 table based on time and place. The time and place are defined by the Investigator as near and far (place), recent and distant (time). The null hypothesis is that all cells will be equal. If the “a” cell (i.e. most recent time and nearest place) is statistically the largest, then there is a disease cluster. In other words, there is a statistical relationship in time and space between the cases. There are several of these statistical tests; some of the most famous are listed by name.