What post tests can Prism perform following two-way ANOVA?

Following two-way ANOVA, there are many possible multiple comparison tests that can help you focus in on what is really going on. However, Prism performs only the post tests described below (which biologists use most frequently).

•	Prism can only compare one value with another value within the same row.

•	Prism does not compare values within the same column.

•	Prism does not compute row means and then compare one row mean with another.

•	Prism does not compute column means and then compare one column mean with another.

Post tests are most often done when there are two columns of data (representing control and treated), and multiple rows (perhaps representing different time points). Prism can perform post tests to compare the control value and the treated value at each time.

If you have three columns, Prism can also perform post tests. Say that data set A is control, data set B is one treatment, and data set C is another treatment. Each row represents a different time point. Prism can do two kinds of post tests. It can do all possible comparisons at each time point (row). In this example, there are three columns, and prism can compare A with B, A with C, and B with C at each row. Or you can specify that one data set is the control (A in this case) and Prism will compare each other data set to the control. In this example, Prism would compare A with B, and A with C at each time point (row).