Re: compound variables - kruskall wallis

Posted by Kirill Orlov on
URL: http://spssx-discussion.165.s1.nabble.com/compound-variables-kruskall-wallis-tp5723154p5723184.html

Diana, you are not correct for Kruskal-Wallis. If you were right about the necessity of equality-of-shapes assumption K-W would have been useless 95% of time. Hopefully, in its general formulation, K-W, like any nonparametric test, requires no distributional assumptions. E.g. http://stats.stackexchange.com/q/76059/3277

K-W is by the way quite close in results (p-value) to ordinal logistic regression with default settings (i.e. logit link, no scale parameter).

20.11.2013 13:02, Kornbrot, Diana пишет:

HI

By compound I assume you mean that variable attitudes is sum of score on 6 items form your batteries?
q1 is attitudes normally distributed? If so can use ANOVA with frequency category as categorical predictor. Chose polynomial in contrasts to check if there is linear rise with frequency category
If not try PLUM read  spss help carefully for interpretation of output. Or google for good internet source on ordinal regression
Why not K-W? Because it assumes that, although not normal , dependent variable has same distributions shape for all 4 categories. This is rare as snowball in hell for summed scales. KW was aimed at variables like time and income that are continuous but long tailed and is widely misused for bounded scales such as your compound scale
Best
Diana


On 19/11/2013 19:11, "Mike O'Driscoll" <odriscollfm@...> wrote:

Thanks Diana
 
Can you or anyone else tell me why Kruskal Wallis is not OK in this case?
 
Thanks
 

From: Kornbrot, Diana [[hidden email]]
Sent: 19 November 2013 17:06
To: Oscar M
Cc: SPSSX(r) Discussion
Subject: Re: compound variables - kruskall wallis

You need ordinal regression also known as plum in spss
Kruskal wallis will not solve your problem


On 19/11/2013 15:43, "Oscar M" <odriscollfm@...> wrote:
Wanting to test a compound variable (i.e. combined 6 variables from a battery
of questions which ask about attitudes to gaming)  against a variable about
frequency of playing games (4 categories). Using kruskall wallis in SPSS but
not sure it is legitimate to use compound variables in this test? Only Non
parametric tests are possible with this data - does not meet any parametric
conditions. All help appreciated.

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Professor Diana Kornbrot
email: : d.e.kornbrot@...
web:    http://dianakornbrot.wordpress.com/
            http://go.herts.ac.uk/diana_kornbrot
Work
Department of Psychology
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---

Professor Diana Kornbrot
email: : d.e.kornbrot@...
web:    http://dianakornbrot.wordpress.com/
            http://go.herts.ac.uk/diana_kornbrot
Work
Department of Psychology
School of Life and Medical Sciences
University of Hertfordshire
College Lane, Hatfield, Hertfordshire AL10 9AB, UK
voice:   [phone]
Home
19 Elmhurst Avenue
London N2 0LT, UK
voice:   [phone]
mobile: [phone]