Two-Way Factorial ANOVA Flashcards
what is two-way ANOVA?
one way ANOVA extended to account for other sources of systematic variation
if 2 types of coffee are brewed (caffeinated and decaf). each is treated with no sweetener, artificial sweetener, or sugar. 12 ppl are randomly and equally assigned to one of the 6 formulations. resting HR is measured after the cup is finished.
what test should be run?
what is the DV? IV?
what are the factors? levels?
a two way factorial ANOVA should be run
DV: HR
IV: caffeination and sweetener
Factor A: caffeination
levels: caf and decaf
Factor B: sweetener
levels: no sweetener, artificial sweetener, sugar
what are the two sources of systematic deviation from the coffee example?
caffeination and sweetener type
what are the two questions to be asked with the coffee example?
what is the effect of caffeination AND sugar on HR?
does the increase caused by caffeine and sugar equal the “sum of the parts”, caffeine and sugar effect?
if the lines of a graph are parallel, what does this mean?
the effect is the sum of the parts
no interaction
if the lines of a graph look like they may intersect if extended, what does this mean?
there is an interaction bw the factors
the effect is NOT a sum of its parts
what is an interaction in two way factorial ANOVA?
it implies that the differences among levels of one factor depends on the level of the other factor
2 IV interact with each other and effect the DV
what are some examples of interactions?
the dif in pain relief bw 2 brands of pain meds may also depend on the medium (gelcap or tablet)
dif in consumption of healthy food among socioeconomic classes (low, middle, upper) may depend on proximity to grocery stores (near or far)
when there are 2 factors that need to be tested, what is the test we use>
two way factorial ANOVA
t/f: each factor in factorial ANOVA has multiple levels
tre
factor A has __ levels and is represented by ___
a, tau
factor B has __ levels and is represented by ___
b, beta
the interaction will have _____ levels and is represented by ___
a x b, tau-beta
what distribution does the two way factorial ANOVA use?
F distribution
what are the assumptions of the two way factorial ANOVA?
independence
normality
homogeneity of variance
what are the hypotheses of the two way factorial ANOVA?
factor A:
- H0: tau1=tau2=…=taua=0 (groups defined by factor A have =means)
- Ha: some taui are not 0 (groups defined by factor B have dif means)
factor B:
- H0: beta1=beta2=…=betab=0 (groups defined by factor B have = means)
- Ha: some betai are not 0 (groups defined by factor B have dif means
interaction term:
- H0: tau-beta1=tau-beta2=…= tau-betaab=0 (no interaction bw factor A and factor B)
- Ha: some tau-betaab are not 0 (interaction bw factor A and factor B)
how many hypotheses are there for two way factorial ANOVAs?
3: 1 about 1 IV, 1 about the other IV, one about the interaction term
what does the factor A null hypothesis say?
no differences among factor A levels
what does the factor B null hypothesis say?
no differences among factor B levels
what does the interaction term null hypothesis say?
there is no interaction