Mann-Whitney U Test

[packersfb]

Hello,

After running a Mann-Whitney U Test on SPSS, some weird results were displayed in the "Ranks" and "Test Statistics" output tables:


Ranks
landvalue
year 1: Mean rank = 16.50, Sum of Ranks = 264.00
year 2: Mean rank = 16.50, Sum of Ranks = 264.00



Test Statistics
landvalue
Mann-Whitney U 128.000
Wilcoxon W 264.000
Z .000
Asymp. Sig. (2-tailed) 1.000
Exact Sig. [2*(1-tailed Sig.)] 1.000b
Exact Sig. (2-tailed) 1.000
Exact Sig. (1-tailed) .515
Point Probability .030

*Grouping Variable: year

I am confused over two things:
1) the "Z" value of 0.000
2) The Asymp. Sig. (2-tailed) value of 1.000

These results do not look right to me, and I believe for some reason the test was not done correctly. Does anyone know of anything i could be doing wrong?

Thanks!

[CowboyBear]

Ranks
landvalue
year 1: Mean rank = 16.50, Sum of Ranks = 264.00
year 2: Mean rank = 16.50, Sum of Ranks = 264.00

If you look at this bit, you can see that the mean ranks are identical in the two groups. I.e. no difference at all. The Z and p values you get entirely make sense in this situation.