Significant test using Mann whitney U test

1. Mann Whitney U test:
- Minimumsample of 7
- Nota normal distribution
- Rankingthem,fromlowesttohighestrank.
Studentcollect/countspeciesXfromtwodifferentarea/fieldusingquadrats/trials
Null hypothesis:Nodifference betweentwospeciesfoundinbotharea1 and 2
ResearchHypothesis:There is difference innumberof speciesfoundfromtwoareasdue to light
intensity
IV – Area1 and area 2
DV – Numberof species.
Number of species X found
Quadrat/trials Area 1 Area 2
1 0 12
2 3 5
3 6 19
4 4 18
5 1 12
6 3 14
7 0 20
Number of species X found Area 1
Quadrat/trials Area 1 Rank them
1 0 0
2 3 0
3 6 1
4 4 3
5 1 3
6 3 4
7 0 6
Number of species X found Area 2
Quadrat/trials Area 2 Rank them
1 12 5
2 5 12
3 19 12
4 18 14
5 12 18
6 14 19
7 20 20

2. Sample calculation
Area Data arranged in ranks, increasing order
1 0 0 1 3 3 4 6
2 5 12 12 14 18 19 20
Area
1
0 0 1 3 3 4 6
Rank
1
1.5 1.5 3 4.5 4.5 6 8 Sum
rank
(R1)
29
Rank
2
7 9.5 9.5 11 12 13 14 Sum
rank
(R2)
76
Area
2
5 12 12 14 18 19 20
U test– formula
U1 (area1) = n1 x n2 + ½(n2) (n2 +1) – SumR1
U2 (area2) = n1 x n2 + ½(n2) (n2 + n1) – SumR2
U1 = 7 x 7 + ½ (7) (8) – 29 = 48
U2 = 7 x 7 + ½ (7) (8) – 76 = 1
U critical isn1= 7 andn2 = 7, givingUcritical value = 8.
Choose lowestUvalues,whichis1.Compare to U critical.If U value issmaller <than U critical,then
there isa significantdifference bettwoareas,andthusrejectnull hypothesisandacceptyour
researchhypothesis.
U critical is 8. U value is1. U value < U critical.
Conclusion:
Uvalue lessthan Ucrit (1 < 8), or P value < 0.05, shows there is significantdifference betweentwo
areas. Reject null hypothesis, acceptalternative hypothesis.
Significance was determinedby U testand P < 0.05, enoughevidence torejectNull Hypothesis,
(significantdifference betweenbothareas)

3. Sample calculation usingonline calculator
Clickhere andhere for online calculator.
Conclusion:- Uvalue lessthan Ucrit (1 < 8), or P value < 0.05, shows there is significantdifference
betweentwoareas. Rejectnull hypothesis, accept alternative hypothesis.
Significance was determinedbyU testand P < 0.05, enoughevidence torejectNull Hypothesis,
(significantdifference betweenbothareas)