To ensure that your results are valid, consider the following guidelines when you collect data, perform the analysis, and interpret your results.
- The response should be numeric
- To calculate the mean response at different factor levels, the multi-vari chart requires numeric response data.
- Each factor should have at least 2 levels
- You may have up to four numeric, text, or date/time factors. Each factor must have at least 2 levels.
- You must have observations for enough factor level combinations
- You need observations for at least 60% of all possible factor level combinations for Minitab to create the chart.
- Suppose you are studying two factors, A and B. Factor A has three levels and Factor B has two levels. There are six possible combinations of factor levels (cells) in this design. If data are not included for one of these combinations, it creates an empty cell (*).
Three of the six factor level combinations, do not have observations. Thus, Minitab cannot create a multi-vari chart.
| C1 |
C2 |
C3 |
| A |
B |
Observations |
| A |
1 |
* |
| B |
1 |
20 |
| C |
1 |
* |
| A |
2 |
22 |
| B |
2 |
* |
| C |
2 |
21 |
| A |
1 |
* |
| B |
1 |
23 |
| C |
1 |
* |
| ... |
... |
... |
