ANOVA

ANOVA

1. ANOVAs Basics

   • Deal with differences between/ among means of a sample
   • No restrictions on the number of means
   • ANOVAs allow more than one IV
   • IVs= factors Conditions= levels of factors
   • Between subject factors: levels vary between participants
   • Within subject factors: levels vary within a participant
   • Reporting findings: F(x,xx)= x.xx, p= (<) xx.xx
   • ANOVA less likely to make a type 1 error than a t-test when there= 2+ IVs

2. F Ratio

   • Variance due to IV/ Error variance = F
   • Small F= error variance larger than IV varience
   • Large F= error variance smaller than IV variance
     • Large F= more likelihood variances caused by IV

3. Degrees of Freedom

   • Two figures need
   • Df- No of levels -1, then N - number of levels

4. Reading (one way) ANOVA output

   • DF: Condition df needed, error df needed. Total= sample size

5. Two-way ANOVA

   • 2 factors
   • x*x e.g 2*2
   • Need 3 sig. tests as= 2 main effects, 1 interaction
   • Examine interaction first, if that not present examine main effects
   • Interaction: the way in which the two factors interact.An interaction is when one variable behaves differently in each condition of the other variable