topic Re: Testing homogeneity for Two-way ANOVA in Statistical Procedures

Testing homogeneity for Two-way ANOVA

rossanaperedo — Thu, 20 Apr 2017 19:37:12 GMT

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?

Re: Testing homogeneity for Two-way ANOVA

Ksharp — Fri, 21 Apr 2017 03:27:53 GMT

Can you try LSMEANS statement ?

And your design is balanced or not balanced ?

Re: Testing homogeneity for Two-way ANOVA

Rick_SAS — Mon, 24 Apr 2017 15:20:22 GMT

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."

Re: Testing homogeneity for Two-way ANOVA

rossanaperedo — Mon, 24 Apr 2017 14:48:20 GMT

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

Re: Testing homogeneity for Two-way ANOVA

rossanaperedo — Mon, 24 Apr 2017 14:50:36 GMT

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

Re: Testing homogeneity for Two-way ANOVA

Hydro1 — Wed, 31 May 2017 20:38:52 GMT

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!

Re: Testing homogeneity for Two-way ANOVA

Rick_SAS — Wed, 31 May 2017 23:04:03 GMT

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