Use a multi-vari chart as a preliminary tool to investigate variation in your data, including cyclical variations and interactions between factors.
The multi-vari chart displays the means at each factor level for every factor. In Minitab, each multi-vari chart can display up to four factors.Minitab uses a different color to show the means and connect lines for each factor.
Step 2: Look for interactions
Multi-vari charts are often used to identify interactions. An interaction occurs when the change in response from one level of a factor to another level depends upon the level of another factor.
For example, suppose a manufacturer produces plastic pipes on two different machines that have three different temperature settings. An interaction between machine and temperature may exist if, for instance, the pipe diameters vary across the temperature settings differently on one machine than the other.