taz=readmatrix('az_solar.xlsx').';
>> [mean(taz) std(taz)]
ans =
138.9109 16.7621
>>
>> mnref=readmatrix('Mean_Surface_REF.xlsx');
>> [mean(mnref); std(mnref)]
ans =
0.0030 0.0065 0.0166 0.0093 0.0013 0.0045 0.0049
0.0034 0.0023 0.0043 0.0034 0.0039 0.0053 0.0052
>>
pretty-much explains it -- the means are some 4-5 orders of magnitude between the one vector and any of the vectors in the array. You've just totally saturated the value of the test statistic to the point the p-value returned is essentially zero.
You'd have been able to determine this yourself if you had simply looked at your data before blindly throwing it at some test statistic.
>> [p,h,stats]=ranksum(taz,mnref(:,1))
p =
8.0633e-44
h =
logical
1
stats =
struct with fields:
zval: 13.8827
ranksum: 25026
>> format long, format compact
>> 1-normcdf(stats.zval)
ans =
0
>> normcdf(stats.zval)
ans =
1
>> normcdf(stats.zval)
ans =
1
>>
