Chapter 12 Flashcards
what is ANOVA
Comparing 3 or more means
how many IV does a one way ANOVA have
1 and 3 or more conditions (levels) of the IV
why should you not use a series of t tests to compare means
multiple t-tests on same data set will increase the probability of making a Type 1 error.
Post hoc test
Only if you reject Ho; tells you which groups are different from each other.
f test
Test to retain or reject the null. are all 3 means the same (retain), or is at least one mean significantly different from another (reject)
statistical hypothesis for ANOVA
Ho: μ1 = μ2 = μ3
Ha: not all μs are equal.
between group variability
Variability due to the IV &
Individual difference/chance
within group variability
Variability due to
individual differences/chance
F ratio, numerator and denominator
between-group variability divided by within-group variability.
what does a higher f ratio mean?
The higher your F-ratio, the bigger the effect of your IV
what does an F of 1 mean
An F = 1 means that the variability between your groups is equal to the variability due to chance.
what does it mean if F<1
F < 1 should not occur, in theory, but will occasionally because the w/in group varibility is > b/group variability. (But F will never be negative.
degrees of freedom between (ANOVA)
k-1 (where k = # of levels of
the independent variable).
df within (ANOVA)
df within: N - k.
(where N = total number of subjects inexperiment, k = # of levels of IV.)
df total ANOVA
N - 1
