# Split-Plot 2-Level Factorial Design

Total factors: Enter the number of factors in the experiment.

Hard-to-Change factors: How many of the factors are hard-to-change (HTC)?

Groups per replicate: How many times can you change the HTC factors in each replicate of the experiment? By default there are enough groups to test all the terms in the resolvable model

Runs per group: How many times can you vary the easy-to-change (ETC) factors at each setting of the HTC factors? These will always be powers of two. This choice will effect the resolution.

Replicates: The value of in this box is the number of times the requested design will be reproduced. The number of runs in the final design is the number of replicates times the number of runs in the requested base design.

Assign one block per replicate: Check the box to put each replicate in its own block.

Group Generator: Only present for designs where the HTC groups of factors form a fractional design. This shows which terms will be tested as HTC factors to achieve the fraction.

Resolution: The roman numerals on this screen are the resolution. They are also color coded such that no color is a full factorial, red are Resolution III, yellow are resolution IV, and green are at least resolution V.

Red means Stop and Think: A resolution III design indicates that main effects may be aliased with two factor interactions. Resolution III designs can be misleading when significant two-factor interactions affect the response.

Yellow means Proceed with Caution: A resolution IV design indicates that main effects may be aliased with three-factor interactions. Two-factor interactions may be aliased with other two-factor interactions. Resolution IV designs are a good choice for a screening design because the main effects will be clear of two-factor interactions.

Green means Go Ahead: Resolution V (or higher) designs are just about as good as a full factorial, while saving some runs. There is an assumption that main effects and two-factor interactions can adequately model the response surface.

Factor Generator: Only present when a fractional factorial design is created. It shows which terms are used to form the fractions. These terms cannot be part of the analysis.

Make generators editable: This advanced option is used to change how the design is created.

Set generators to defaults: Restores the default generators, if the editing doesn’t go as planned.

Click Next >> to enter factor details.