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## Remember

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**Remember**• You were asked to determine the effects of both college major (psychology, sociology, and biology) and gender (male and female) on class attendance**Simple Effects**• The effect of one factor at one level on the other factor. • Use to “tease apart” a significant interaction • You wonder if college major has an effect on class attendance for just females? • You wonder if male and female psychology students differ in their class attendance?**Simple Effects**• Why not just do 5 new analyses • 2 ANOVAs • 3 Independent Samples t-tests • You will lose df! • Type I error problem still exists**Simple Effects**• SS Major at Female • Represents the SS deviations of the treatment means around the Female mean • Its multiplied by n to give an estimate of the population variance (Central limit theorem) • Same formula as SSbetween in the one-way**SS M at Female = 3*((2.67 – 1.78)2 + (1.00 – 1.78)2 +**(1.67 – 1.78)2 = 4.23**Simple Effects**• SS Major at Male • Same formula as SSbetween in the one-way**SS M at Male = 3*((3.67 – 2.33)2 + (3.00 – 2.33)2 +**(0.33 – 2.33)2 = 18.71**Simple Effects**• SS Gender at Socio • Same formula as SSbetween in the one-way**Simple Effects**• SS Gender at Psych • Same formula as SSbetween in the one-way**Simple Effects**• SS Gender at Bio • Same formula as SSbetween in the one-way**Simple Effects**dfA (Gender) = a – 1 dfB (Major) = b – 1**Simple Effects**Compute MS**Simple Effects**Compute F**F critical (1, 12) = 4.75**F critical B (2, 12) = 3.89 Simple Effects**Practice**• ANOVA is from exercise 13.5 • 1) Interpret the ANOVA results • 2) Plot the cell means • 3) Compute an entire set of simple effects