Two-Way Between Groups ANOVA

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# Two-Way Between Groups ANOVA - PowerPoint PPT Presentation

Two-Way Between Groups ANOVA. Chapter 14. Two-Way ANOVAs. Are used to evaluate effects of more than one IV on a DV Can determine individual and combined effects of the IVs. The basic 2 WayANOVA situation. 2 or more Nominal Independent Variable with two or more levels

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### Two-Way Between Groups ANOVA

Chapter 14

Two-Way ANOVAs
• Are used to evaluate effects of more than one IV on a DV
• Can determine individual and combined effects of the IVs
The basic 2 WayANOVA situation
• 2 or more Nominal Independent Variable with two or more levels
• 1 Scale Dependent Variable
• Effects of Drug and Age on recovery time
• Effects of Exercise and Diet on number of friends
• Effects of Toy Color and Gender on toy popularity
One Way ANOVA is Limited
• Previous data, hour of exercise by relationship status. If I want to look at sex differences for hours of exercise, I have to do a second one-way ANOVA, and it will not tell me if there is a connection between sex and relationship status on hours of exercise.
Testing for Interactions
• An interaction occurs when two IVs have an effect in combination that we do not see when looking at each IV individually
• Two-Way ANOVAs include to nominal IVs and a scale DV
• Factorial ANOVA uses one scale DV and at least two nominal IVs (factors)
• Factor: IV in a study with more than one IV
Why Use Two-Way ANOVAs
• To evaluate effects of two IVs, it is more efficient to do a single study than two studies with one IV each.
• Can explore interactions between variables
More ANOVA Vocabulary
• Cell: box depicting a unique combination of levels of IVs in a factorial design
• Main effect: When one IV influences the DV
Two Types of Interactions in ANOVA
• Quantitative: interaction in which one IV exhibits strengthening or weakening of its effects at one or more levels of the other IV, but the direction of the effect does not change
• Qualitative: interaction of two or more IVs in which one IV reverses its effect depending on the level of the other IV
Understanding Graphs
• Main Effects: distance between lines
• Quantitative
Understanding Graphs
• Interactions: slopes of lines
• Qualitative
Six Steps for Two-Way Between-Groups ANOVA
• Step 1. Identify the populations, distribution, and assumptions.
• Step 2. State the null and research hypotheses.
• Step 3. Determine the characteristics of the comparison distribution.
• Step 4. Determine critical values, or cutoffs.
• Step 5. Calculate the test statistic.
• Step 6. Make a decision.