Two way between groups anova
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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. Testing for Interactions.

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Two way anovas
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

Testing for interactions
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
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
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
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

What if both ivs influence the dv
What if both IVs influence the DV?

  • This is an interaction

Six steps for two way between groups anova
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.

Df formulae for anovas
df Formulae for ANOVAs