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04-20-2017 03:37 PM

Hi,

I am trying to test homogeneity for a two way ANOVA, (linearity assumption was alreay verified), but It doesn't work, I read that Levene's test is only for one way ANOVA

PROC GLM DATA=clus_ConHR;

CLASS Cluster agegroup;

MODEL vitesse_trt = Cluster agegroup Cluster*agegroup;

means Cluster*agegroup/ HOVTEST=levene(type=ABS);

run;

quit;

How should I test homogeneity using SAS in this model? Should I construct a plot with the residuals?

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Solution

04-26-2017
02:03 PM

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04-24-2017 10:50 AM

I was trying to test homogeneity of variance by looking at the distributions. I found this solution:

PROC glm DATA=clus_ConHR;

CLASS Cluster agegroup;

MODEL fct_executive = Cluster agegroup Cluster*agegroup;

output out = residus p=predit rstudent=rstudent;

run;

quit;

Proc gplot data = residus;

plot rstudent* (predit);

run;

Thank you

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04-20-2017 11:27 PM

Can you try LSMEANS statement ?

And your design is balanced or not balanced ?

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04-24-2017 10:48 AM

Lsmeans didn't gave me the results that I need to test homogeneity. Thank you anyway.

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04-21-2017 10:58 AM - edited 04-24-2017 11:20 AM

Not clear if you want a statistical test or a graph that enables you to visually check distributions. For a graph, try using the EFFECTPLOT statement:

```
proc genmod DATA=clus_ConHR;
CLASS Cluster agegroup;
MODEL vitesse_trt = Cluster agegroup Cluster*agegroup
effectplot box / cluster;
run;
```

For details and a discussion, see "Visualize an ANOVA with two-way interactions."

Solution

04-26-2017
02:03 PM

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04-24-2017 10:50 AM

I was trying to test homogeneity of variance by looking at the distributions. I found this solution:

PROC glm DATA=clus_ConHR;

CLASS Cluster agegroup;

MODEL fct_executive = Cluster agegroup Cluster*agegroup;

output out = residus p=predit rstudent=rstudent;

run;

quit;

Proc gplot data = residus;

plot rstudent* (predit);

run;

Thank you

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05-31-2017 04:38 PM

Although the graphics (expecially boxplots) are useful in assessing homogeniety of variance across groups in a 2-way ANOVA, I am looking for a statistical test that can be applied ? Most of what I have seen only applies to 1-way ANOVA ?

Thanks for your help!

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05-31-2017 07:04 PM

For a discussion of two-way tests of homogeneity of variance, see the examples and discussion at

http://www.stat.wmich.edu/wang/664/egs/SASsoybean.html