# PSYC 3000 Lecture Notes - Lecture 3: Explained Variation, Analysis Of Variance, F-Test

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2 Aug 2016

School

Department

Course

Professor

PSYC 3000

Jan 14

ANOVA

-generalization of the t test

-can have more than two groups

-variable must still be interval or better

Strategy of t test

-an anova with only two groups, it is basically a t test

-s pooled is characterising unexplained variation within a group

-numerator measures explained variation between groups

-variation between groups is caused by a successful treatment

Between variability

-we use the variance of all the groups

-if the means are all very separate and the variance will be big

-once anova is completed and a difference between groups is notice, then t tests are used

Value of F

-if I take variance of means and multiply it by sample it turns into estimate of population variance

-both numerator and denominator are estimates of population variance. So they should be the same if

the null hypothesis is true. Hence, F = 1 if Ho is true.

-in assignment 4. The ANOVA test should reveal that the null hypothesis is false. So further testing must

be done to find out which groups are significantly different.

-F needs to have a critical point in which we can have limits of accepting the null hypothesis

-critical point is usually at 5%.

-F test is always one tailed.

ANova calculations table

-between groups is the numerator

-within is denominator

-mean square is anova speak for variance

-read slide 43 of week 15 to know how to report anova in assignment

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