# ANOVA with Optimal Scaling technique and unequality of variance

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## ANOVA with Optimal Scaling technique and unequality of variance

 Hi, I'm a PhD student in Ecology. I've got experiments that follow a two- way ANOVA design. My variances are unequal even after classic transformation (sqrt, Log). I would like to use ANOVA using the Optimal Scaling technique available on SPSS. Does ANOVA with optimal scaling require equal variances? Thank you. Sébastien.
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## Re: ANOVA with Optimal Scaling technique and unequality of variance

 I guess you mean regression using optimal scaling (CATREG)? with nominal scaling level voor dependent variable this is ANOVA. No equal variances required. Regards, Anita van der Kooij Data Theory Group Leiden University -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Sebastien Sent: 15 June 2006 13:42 To: [hidden email] Subject: ANOVA with Optimal Scaling technique and unequality of variance Hi, I'm a PhD student in Ecology. I've got experiments that follow a two- way ANOVA design. My variances are unequal even after classic transformation (sqrt, Log). I would like to use ANOVA using the Optimal Scaling technique available on SPSS. Does ANOVA with optimal scaling require equal variances? Thank you. Sébastien. ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. **********************************************************************
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## Re: ANOVA with Optimal Scaling technique and unequality of variance

 In reply to this post by Sebastien-6 Thank you for your answer. I've got some further questions: 1) Do you have any reference I can use to justify that equal variances is not required? 2) Are there any assumptions behind optimal scaling? 3) What are the risks of type 1 and 2 errors with the optimal scaling technique when the data have not equal variances? It has been suggested to me to use Aligned Rank Transformation to study interaction effect in a two-way ANOVA design, but it appeared that this method is not suitable when variances are not equal, which is the case of my data. That's why I'm looking for another method and I want to make sure that this method can be used with confidence. Sébastien.