research methods advanced- mixed anova

main effects

refer to the influence of one IV irrespective of the others

interactions

refer to how the effect of one variable depends upon the other. a significant interactions shows that the effect of one IV cannot be understand unless the other IV is taken into account

post hoc tests

used to understand the main effects if the IV has more than 2 levels. post hoc tests are needed to understand where the significant differences are

mixed anova

one IV is manipulated between participants, one IV is manipulate within participants

two way mixed anova output

the main effect of the within- subjects IV is in the tests of within subjects effects table. the main effect of the between subjects IV is in the tests of between subjects effects table. post-hoc tests for thw within subjects IV (bonferroni) post hoc tests will be in the pairwise table

basic structure of reporting an ANOVA

1.descriptive statistics

2.results of ANOVA (main effect of IV1,main effect of IV2, interaction)

3.interaction plot

assumptions of parametric tests

-normally distributed data

-homogenity of variance

-ratio or interval data

(ANOVA is robust to violations of normality and homogentity of variance as long as group sizes equal)

tests of normality

if the skew and kurtotis are between -1 and +1 then its ok

tests of homogentity of variance

levenes test in SPSS, the rule of four (howell)- take the largest standard deviation and divide it by the smallest standard deviation. if its less than 4 the data have met the homogeneity of variance assumption

non parametric tests

no parametric test equivilant to multi way anova. havbe to split the analaysis into main effects and analyse each main effect seperately. interactions cannot be tested using a non parametric test. choice of non parametric tests depend on how many conditions are within the IV

kRUSKAL WALLIS TEST

for ivs with 3 or more conditions

friedmans test

for IVs with 3 or more conditons wwithin subjects design

Mann- whitney U test

for IVs with 2 conditions , between subjects design

wilcoxons test

for IVs wutg 2 conditions within subjects design