factoral designs
DESCRIPTION
Factoral DesignsTRANSCRIPT
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Factorial Designs
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A Simple ExampleTime in Instruction1 hour per week4 hours per weekSettingIn-classPull-outRX11ORX12ORX21ORX22OFactor 1:Level 1:Level 2:Factor 2:Level 1:Level 2:
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A Simple ExampleTime in InstructionSetting
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A Simple ExampleTime in InstructionSettingFactors:Major independent variables
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A Simple ExampleTime in InstructionSetting1 hour/week4 hours/weekIn-classPull-out
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A Simple ExampleTime in InstructionSetting1 hour/week4 hours/weekIn-classPull-outLevels:subdivisions of factors
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A Simple ExampleTime in InstructionSetting1 hour/week4 hours/weekIn-classPull-out
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A Simple ExampleTime in InstructionSetting1 hour/week4 hours/weekIn-classPull-outA 2(rows) x 2 (columns) design
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A Simple ExampleTime in InstructionSetting1 hour/week4 hours/weekIn-classPull-outThere are 4 (i.e., 2x2) groups.
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A Simple ExampleGroup 2averageGroup 4averageGroup 1averageGroup 3averageTime in InstructionSetting1 hour/week4 hours/weekIn-classPull-outUsually, averages are in the cells.
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Multiplicative NotationA 3 x 4 factorial design
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Multiplicative NotationA 3 x 4 factorial designThe number of numbers tellsyou how many factorsthere are.
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Multiplicative NotationA 3 x 4 factorial designThe number of numbers tellsyou how many factorsthere are.There are 2 factors because there are 2 numbers.
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Multiplicative NotationA 3 x 4 factorial designThe number values tell youhow many levels are ineach factor.
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Multiplicative NotationA 3 x 4 factorial designThe number values tell youhow many levels are ineach factor.Factor 1 has 3 levels.Factor 2 has 4 levels.
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The Null Case555555551 hr4 hrsOutInTimeSettingThe lines in the graphsbelow overlap eachother.
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A Main EffectA consistent difference between levels of a factorFor instance, we would say theres a main effect for setting if we find a statistical difference between the averages for the in-class and pull-out groups
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Main Effects575766571 hr4 hrsOutInTimeSettingMain Effect of Time
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Main Effects557757661 hr4 hrsOutInTimeSettingMain Effect of Setting
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Main Effects577968681 hr4 hrsOutInTimeSettingMain Effects of Time and Setting
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An Interaction EffectWhen differences on one factor depend on the level you are on on another factorAn interaction is between factors (not levels)You know theres an interaction when cant talk about effect on one factor without mentioning the other factor
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Interaction Effects555756561 hr4 hrsOutInTimeSettingThe in-class, 4-hour perweek group differsfrom all the others.
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Interaction Effects755766661 hr4 hrsOutInTimeSettingThe 1-hour amount workswell with pull-outs whilethe 4 hour works as wellwith in class.
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Advantages of Factorial DesignsOffers great flexibility for exploring or enhancing the signal (treatment)Makes it possible to study interactionsCombines multiple studies into one
why use factorial designs?efficient -- combine several studies in onethe only way you can investigate interactions