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Community Trekker

## Testing for independence in ANOVA

Hi

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?

Thanks!

Nikolaj

1 ACCEPTED SOLUTION

Accepted Solutions
Staff (Retired)

## Re: Testing for independence in ANOVA

ANOVA assumptions
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

11 REPLIES 11
Staff (Retired)

## Re: Testing for independence in ANOVA

ANOVA assumptions
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

Community Trekker

## Re: Testing for independence in ANOVA

Thanks. So for the test of independence in errors i simply make a column from 1 to how many?

Staff (Retired)

## Re: Testing for independence in ANOVA

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.

Community Trekker

## Re: Testing for independence in ANOVA

Here is a screen shot of how it looks when I am in fit y by x. I cannot see quality and reliability anywhere?

Staff (Retired)

## Re: Testing for independence in ANOVA

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.

Staff (Retired)

## Re: Testing for independence in ANOVA

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

Community Trekker

## Re: Testing for independence in ANOVA

Hello Lou Valente,

Where test for equality of variances?

Staff (Retired)

## Re: Testing for independence in ANOVA

Go to red triangle and select Unequal Variances....

Community Trekker

## Re: Testing for independence in ANOVA

Thanks Lou Valente. For mixed effects models have the option to test homogeneity? Or only one way Anova?