Complete the following steps to examine the properties of the design. Key outputs include the design summary and the alias structure.

Use the summary of the design to examine key design properties. Most properties of the design match selections that you made for the base design. Whole-plot replicates and subplot replicates increase the number of runs in the design.

Factors: | 4 | Whole plots: | 4 |

Hard-to-change: | 1 | Runs per whole plot: | 8 |

Runs: | 32 | Whole-plot replicates: | 2 |

Blocks: | 1 | Subplot replicates: | 1 |

In these results, 16 runs form a full factorial design among the 4 factors in the design. Two whole-plot replicates doubles the number of runs in the design to 32 runs.

The alias structure describes the confounding pattern that occurs in a design. Terms that are confounded are also said to be aliased.

Aliasing, also known as confounding, occurs in fractional factorial designs because the design does not include all of the combinations of factor levels. For example, if factor A is confounded with the 3-way interaction BCD, then the estimated effect for A is the sum of the effect of A and the effect of BCD. You cannot determine whether a significant effect is because of A, because of BCD, or because of a combination of both. When you analyze the design in Minitab, you can include confounded terms in the model. Minitab removes the terms that are listed later in the terms list. However, certain terms are always fit first. For example, if you include blocks in the model, Minitab retains the block terms and removes any terms that are aliased with blocks.

You can use the alias structure to verify that important terms are not aliased with each other. If the alias structure is unacceptable, consider taking one of the following actions:

- Create the design again, but enter the factors into Minitab in a different order.
- Use a larger fraction of the design.

To see how to determine the alias structure, go to All statistics for Create 2-Level Split-Plot Design and click "Defining relation".

Factors: | 5 | Whole plots: | 4 | Resolution: | IV |

Hard-to-change: | 1 | Runs per whole plot: | 4 | Fraction: | 1/2 |

Runs: | 16 | Whole-plot replicates: | 1 | ||

Blocks: | 1 | Subplot replicates: | 1 |

Design Generators: E = ABC

Hard-to-change factors: A

Whole Plot Generators: A, DE

Whole plots are confounded with the following terms: DE, ADE, BCD, ABCD

I + ABCE |
---|

A + BCE |

B + ACE |

C + ABE |

D + ABCDE |

E + ABC |

AB + CE |

AC + BE |

AD + BCDE |

AE + BC |

BD + ACDE |

CD + ABDE |

ABD + CDE |

ACD + BDE |