Tagged Questions

3
votes
1answer
105 views

QQ plot is consistent with normality when subgroups are non-normal

I have read that for a one way ANOVA, you should check that the model residuals are normally distributed. If the variance of each group is homogeneous then this implies that the residuals with each ...
0
votes
1answer
459 views

Normality test for anova mixed model in SPSS: I did it in two ways but the results are contrasting

I'm conducting an ANOVA mixed model 2 X 3 (group X condition). Right now, I'm checking for the assumptions of ANOVA, such as normality. I should check indipendently for group and condition, right? I ...
1
vote
0answers
131 views

Significant factor in 2-way repeated ANOVA becomes not significant in 3-way repeated ANOVA?

My research design is 2(Ear) x 3(Factor A) x 3(Factor B) with repeated measures on all factors. For 2 way-repeated ANOVA, I used laterality index (normal distribution, calculated from % of responses ...
1
vote
2answers
2k views

Testing normality assumptions for linear mixed models and mixed (repeated) GLM ANOVA in SPSS

I have a mixed design that includes both repeated (condition) and between (sex and genotype) subjects factors. I would like to assess whether my data meets the normality assumptions for 1) General ...
2
votes
2answers
2k views

Repeated measures ANOVA or Friedman test?

I have a study with 35 subjects who received hypercoagulability testing at 4 different times (before surgery, after, at 1 week, and at 1 month). Each subject has 9 different test of hyper ...
3
votes
2answers
3k views

How robust is ANOVA when group sizes are unequal and residuals are not normally distributed?

I understand that there are degrees of trust one can have in the output of ANOVA. However, naturally I want to maximize the amount I can trust my results. Question: If I have data that violate the ...
4
votes
2answers
2k views

How to test for normality in a 2x2 ANOVA?

Study Design: I showed participants some information about sea-level rise, focusing the information in different ways, both in terms of the time-scale and the magnitude of potential rise. Thus I had a ...
2
votes
3answers
1k views

How robust is ANOVA to violations of normality?

I have several dependant variables that are non normal in distribution: Kolmogorov-Smirnov test is significant, skewness ranges up to 8 for some variable, and kurtosis is generally about 2 but in a ...
2
votes
3answers
2k views

Whether to report untransformed data when performing ANOVA on transformed data?

I'm trying to understand how to analyse transformed data using ANOVA. If my data does not meet the assumption of normality, and I have transformed it using a log transformation to fix that, would I ...
4
votes
3answers
2k views

Testing the normality assumption for repeated measures anova? (in R)

So assuming that there is a point in testing the normality assumption for anova (see 1 and 2) How can it be tested in R? I would expect to do something like: ...
9
votes
4answers
12k views

Can I trust ANOVA results for a non-normally distributed DV?

I have analyzed an experiment with a repeated measures ANOVA. The ANOVA is a 3x2x2x2x3 with 2 between-subject factors and 3 within (N = 189). Error rate is the dependent variable. The distribution of ...
17
votes
5answers
3k views

If the t-test and the ANOVA for two groups are equivalent, why aren't their assumptions equivalent?

I'm sure I've got this completely wrapped round my head, but I just can't figure it out. The t-test compares two normal distributions using the Z distribution. That's why there's an assumption of ...