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 ...
3
votes
1answer
129 views

ANOVA:How to detect non-normality with a QQPlot in the presence of non-homogeneous variance

This is a pretty general question but, I often find statistical textbooks claiming that, in order to justify the within groups normality assumption of a one way ANOVA, you can look at a QQ plots of ...
2
votes
1answer
128 views

Should raw data or residuals be used to check homogeneity of variance?

Unexpectedly for me (!) I've recently learnt that: "We have assumed that the error terms, $\epsilon_{ij}$, of the variates in each sample will be independent, that the variances of the error terms ...
3
votes
0answers
208 views

Simultaneous heteroscedasticity and heavy tails in a regression model

I'm trying to create a prediction model using regression. This is the diagnostic plot for the model that I get from using lm() in R: What I read from the Q-Q plot is that the residuals have a ...
3
votes
2answers
347 views

Model errors, residuals and heteroscedasticity

I have a quick question about the correct way to describe variance functions when seeking to cope with heteroscedasticity. As I understand it the statistical error of a model represents the departure ...
8
votes
3answers
942 views

Advice on explaining heterogeneity / heteroscedasticty

I am looking for any help, advice or tips in how to explain heterogeneity / heteroscedasticity to biologists in my department. In particular I want to explain why its important to look for it and deal ...