I am sure I am opening myself up to looking stupid, but  I have two samples
with medians of 613.5  and 189 (difference in location of 424 compared to
the difference suggested from the wilcoxon of 291.5)

> wilcox.test(pipwtCount,pipwdCount, conf.int=TRUE, na.rm=TRUE)

    Wilcoxon rank sum test

data:  pipwtCount and pipwdCount
W = 822, p-value = 0.01227
alternative hypothesis: true location shift is not equal to 0
95 percent confidence interval:
  58 639
sample estimates:
difference in location
                 291.5

The data is here

> pipwtCount
 [1]  532  298  215 1588   38  180  284  376 5349 1024  650  605 1307 6147
21
[16]  453   23 1983 1048  464 2183 1028 1361  163  175 5944  569  622  793
70
[31]   67 1188  248 3010   19 2179 1339  408  113  739 2615 4619

> pipwdCount
 [1]   89  384   12  703    2  138  189  383  314  482   96  907   90 1193
154
[16]  305   61  414 4764 1066  121  143  102  174   44 2896   NA 1103  161
199

> median(pipwtCount)
[1] 613.5
> median(pipwdCount,na.rm=T)
[1] 189
> 613.5-189
[1] 424.5


I would appreciate if someone could point out the obvious to me, and explain
why there is such a large discrepancy in the differences in location.



Many thanks,

Graham

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