Hi All,
I have asked some students to use SPSS to analyse some data from Pallant’s book ‘the SPSS survival manual’ and I am working through the questions myself. I’ve asked the students to examine whether there is any relationship between educational status (ranging from not much education – running through to higher degree level) which can be considered an ordinal variable, and marital status (married, single, divorced, widowed etc.) – which really seems to be a categorical variable.
In doing the examples though, some thoughts/problems occur to me, which probably have a simple answer, though right now – I can’t see it!
I initially decided to group educational status, using marital status as the factor and apply a Kruskal-Wallis test. This test gives a ‘non significant’ result. Next I decided to apply a Chi-Square analysis treating both variables as categorical and this time both the pearson’s and likelihood ratio variants of the test say that there is a highly significant result.
OK – two questions.
First – is there any good reason why kruskal-wallis (which I would have taken as being the more powerful technique) doesn’t show significance when the chi-squared tests do (in other words, am I correct in my assumptions as to which is the more powerful technique).
Secondly chi-squared provides a ‘symmetrical’ analysis – it says (at least I think that it does) that having information about one of the variables provides information about the other variable – and vice versa. However is Kruskal-Wallis ‘symmetrical’ in this sense. Does not KW say (had it been significant) that the marital status of the subjects (the factor) informs us somewhat on their educational status (the dependent variable). Now logically if this is true then the educational status should inform us somewhat on the marital status, however is this also the case ‘statistically’ i.e. will any significance level generated by the KW using education (dependent) v marital status (independent) also apply to phrasing the question the ‘other way around’?
I hope that what I’ve written makes some kind of sense. I appreciate that this might be a ‘simple’ or even ‘stupid’ question (I have these 'blips' every now and again) but I’d like to get it clear in my own head before approaching the students with what I think is the ‘right answer’.
Best Regards and Many Thanks
Graham
-- Dr G.S.Clarke Lecturer in Physiology & Biometry Faculty of Health Studies University of Wales, Bangor Fron Heulog Ffriddoedd Road Bangor Gwynedd LL57 2EF
Tel: 01248 383157 e-mail: [EMAIL PROTECTED]
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