Psych 301 Lecture 15 Factorial Variations PDF

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Psych 301 Lecture 15 Factorial Variations...

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Psych 301

Lecture 15

Factorial Variations

Independent-Groups Factorial Design • Also known as between-subjects, or between-groups, factorial design • All IVs are manipulated between groups • A 2 x 2 independent-groups factorial design has four groups/cells. • If I have a 2 x 2 independent-groups factorial design and I want 50 participants in each cell, how many participants do I need in total? – 200

Within-Groups Factorial Design • Also known as within-subjects, or repeated-measures, factorial design • All IVs are manipulated within subjects • A 2 x 2 within-groups factorial design has four cells, but all participants participate in all four cells. • If I have a 2 x 2 within-groups factorial design and I want 50 participants in each cell, how many participants do I need in total? – 50

Mixed Factorial Design • Combination of independent-groups design and within-groups design • One (or more) IV is manipulated between subjects, and one (or more) IV is manipulated within subjects • A 2 x 2 mixed factorial design has four cells, with all participants participating in two cells. • If I have a 2 x 2 mixed factorial design and I want 50 participants in each cell, how many participants do I need in total? – 100

Increasing the Number of Levels of an Independent Variable • Sometimes you need more than two levels of an IV. • Factorial designs are notated like this: ___ x ___. - Number of blanks = number of IVs - Numbers in the blanks = number of levels of each of the IVs

Increasing the Number of Independent Variables • Sometimes you need more than two IVs. • A design with three IVs is called a three-way design. • What is the notation for the design below? – 2 x 2 x 2 Does the interaction between age and cell phone use depend on traffic? If so, then you have a three-way interaction!

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