MANE 6313

Week 6, Module C

Student Learning Outcome

• Select an appropriate experimental design with one or more factors,
• Select an appropriate model with one or more factors,
• Evaluate statistical analyses of experimental designs,
• Assess the model adequacy of any experimental design, and
• Interpret model results.

Module Learning Outcome

Interpreting interactions in factorial designs.

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Interaction Analysis for Problem 5.9

Recall

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Rules for Interpreting Interactions

Limited to models with two-factor interactions and main effects

1. If an interaction is statistically significant for a two-factor interaction, use the interaction plot to select the optimal setting
2. If the interaction is not statistically significant for a two-factor interaction, use the main effect plot to select the optimal setting
3. More sophisticated designs are more difficult to interpret

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Interaction Plot

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Comments on Example Interaction Plot

• Lines are not parallel, therefore interaction is statistically significant
• Maximum surface finish is found when Feed Rate = 0.3 and Depth of cut is 0.25
• Minimum surface finish is found when Feed Rate=0.2 and Depth of cut is 0.15

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Main Effect Plot for Feed Rate

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Main Effect Plot for Depth of Cut

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R Demonstration