how to arrange data in Mann - Whitney U test

sk2

New Member
#1
Hi,
I have a data for pH of groundwater samples from four sites in first season and three sites in second season. I wanted to apply the Mann whitney U test to compare the groups.

In first season raw data of pH for four sites analysed in triplicate and mean value for site are as follows:
Site 1
7
7
7
Mean = 7
Site 2
6
7
7
Mean = 6.67
Site 3
7
7
8
Mean = 7.33
Site 4
7
8
8
Mean = 7.67

In second season raw data of pH for three sites analysed in triplicate and mean value for site are as follows:
Site 1
7
7
7
Mean = 7
Site 2
7
7
8
Mean = 7.33
Site 3
6
6
8
Mean = 6.67
When comparing these two seasons using mann whitney u test, should I use all triplicate values (as n = 4 x 3 = 12, for first season and n = 3 x 3 = 9, for second season) or I should use means for four sites in first season (n = 4) and three sites in second season (n = 3). What is correct method?
Please help me!
Thanks in advance!!!
Sk2