Irregular Fraction Design
These are two-level resolution V designs that use unusual fractions like 3/4, 3/8, etc. of the number of runs that a full factorial would need. Resolution V designs allow you to estimate the main effects and the two-factor interactions. (Other Resolution V designs are color coded "green" on the 2-Level Factorial screen.)
There are three sequential screens involved in building an irregular fraction design. In the first screen you select the number of factors and assign names, units, types, and levels. You may also add center points to the design. If you are going to run center points, we recommend adding 4 or 5 to get an adequate test for curvature and lack of fit. The second screen displays information about the design including aliasing of the factors and interactions. Enter your expected response names and units on the third screen.
Tip: When selecting effects by using the Half-Normal Probability plot, the positioning of the effects may shift, depending on the other terms selected. It is very important to use the Re-Calculate button and the ANOVA to confirm the selection of terms.
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After the screen that displays the alias structure (if one exists), is a screen that has a table for factor names, units, factor type, and levels. Enter the factor information. Factor type can be either numerical (continuous scale) or categoric (class or label.) Click Continue again to enter the response names and units of measurement. Click Continue once more to build the design.