I am conducting an ANOVA and I am in the process of performing the assumption checks.
I have checked for normality and homogeneity of variance. However, I am not sure about how
to create a scatter plot in order to test for independence of errors.
In my research design respondents have been divided on the basis of what type of coke they
drink (diet or regular), on a colour basis (red or green), and on an information basis (little or much).
They have for instance answered a question about the attractiveness of the product under study
on the basis of a 5-point likert scale. With this information then how do I test for independence of
errors in SAS JMP?
1.) Errors normally distributed>Save residuals and run distribution, normal quantile plot and fit normal>goodness of fit
2.) Variance are the same for all groups> Test for equal variances
3.) Errors occur independently>Plot residuals over time
One way to accomplish this is if you are in the fit Y by X platform or fit model you can save your residuals and the under quality and reliability you can create a run chart or even an IR chart to display the residuals over time.
I apologize for the confusion. Once you save your residuals to your data table from the Fit Y by X, you can launch the Analyze>Quality and Process platform and create a run chart and or/IR from there.
Since I am not exactly clear on your specific problem I would suggest some good references that can easily found by searching google by entering
Testing for Independence of Errors in ANOVA in JMP