STAT-4204 - Notes - 8 - Factorial Treatment Interactions PDF

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Prof: AR Driscoll...

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Daniel T. Eisert

STAT-4204

8 – Factorial Treatment Interactions (Ch. V) STAT-4204: Experimental Designs September 19, 2019 (Week 4)

Class Business Interaction

Homework III due on Monday, September 23 at 11:59 P.M. Test Review in-class on Tuesday, September 24th. Test I is Thursday, September 26th in class. Review the practice question. Changes in Factor A result in changes in Factor B. Insignificant

Significant B Main Effect A

A Positive main effect ( ↑ A , ↑ B ) response

A A only has an effect on the at the higher level of B Interaction more at the higher level of B

Recall ~ tests are data dependent (i.e., how many observations, how many replications) Significant (both of these plots have the same interpretation)

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Antidirectional A × B interaction is significant Changing one factor changes the response, but this is not seen by the main effect (shown in gray). Recall that the main effect is just the average of A (blue) and B (red). Amain will be insignificant, but we can see that it DOES affect the response (only the main effect will be insignificant). Significant interactions can mask the overall/main effects. Masking is more common in antidirectional interactions.

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