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Activity Number:
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231
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Type:
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Contributed
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Date/Time:
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Monday, August 3, 2009 : 2:00 PM to 3:50 PM
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Sponsor:
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Section on Statistical Consulting
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| Abstract - #304550 |
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Title:
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Testing for Co-Directional and Anti-Directional Interactions Using Union-Intersection and Intersection-Union Methods
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Author(s):
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Julia L. Sharp*+ and Patrick D. Gerard
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Companies:
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Clemson University and Clemson University
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Address:
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237 Barre Hall, Clemson, SC, 29634-0313,
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Keywords:
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Factorial ; Simple Effects
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Abstract:
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When significant interaction terms exist in a two-factor, factorial experiment, the consideration and analysis of main effects is often restricted to those situations where the interaction between factors is not significant. Hinkelman and Kempthorne (1994) softened that stance somewhat and advocate testing main effects when the interaction is deemed co-directional but not anti-directional. A test for the main effects may be pragmatic to the practitioner and instructor. Intersection-union and union-intersection methods are examined for assessing the directional nature of significant interactions so that the main effects in a two-factor factorial may be evaluated. The methods suggested are conceptually straightforward and practical and are illustrated through example.
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