It's best to think of this in ROC terms. The ROC curve has to pass through (0, 0) and (1, 1) anyway. Identical medians implies it also passes through (0.5, 0.5). But, although constrained by these 3 points, one or both halves of the curve must lie substantially above the main diagonal. It is quite possible to construcy sets of numbers that satisfy this constraint. But I think it would be difficult to find a convincing real example in which such a departure from H0 would be plausible.
Robert Newcombe
Cardiff
-----Original Message-----
From: A UK-based worldwide e-mail broadcast system mailing list [mailto:[log in to unmask]] On Behalf Of MACDOUGALL Margaret
Sent: 29 August 2018 21:34
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Subject: Mann-Whitney U-test illustrations for special case only, please
Hello
I am in search of good illustrations for teaching purposes where for two groups, the medians are identical but when the two groups are compared using the Mann-Whitney U-test, there is a significant difference between these groups.
Thanks in advance
Best wishes
Margaret
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr Margaret MacDougall
Medical Statistician and Researcher in Education (Senior Lecturer) Centre for Population Health Sciences The Usher Institute of Population Health Sciences and Informatics University of Edinburgh Medical Shool Teviot Place Edinburgh EH8 9AG
Tel: +44(0)131 650 3211
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https://www.ed.ac.uk/profile/margaret-macdougall
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