Mann Whitney U Test | Statistics

The Mann Witney U Test in statistics is related to a testing without considering any assumption as to the parameters of frequently distributed of a valueless hypothesis. It is similar to the value selected randomly from one sample, can be higher than or lesser than a value selected randomly from a second sample. Copy the link given below and paste it in new browser window to get more information on Mann Whitney U Test:- http://www.transtutors.com/homework-help/statistics/mann-whitney-u-test.aspx

1. The Man Whitney U-test

2. What is the Mann Whitney U-
test?
It is a nonparametric test .It is used to analyse the difference
between the medians of different data sets. The critical
values tables is used to assess the degree of difference
The Mann Whitney U-test can be used if the answer to the
below questions is ‘yes’
•Are you investigating the difference between two samples
of data?
•Is the data nonparametric?
•Is the data ordinal?
•Are there more than five pieces of data in each sample?
•Are there 20 or fewer pieces of data in each sample
(recommended)?

3. Mann Whitney U-test :
Application
Analysing the traffic flows
Analysing the impact of retail development upon traffic and
the local area. primary data was collected in two parts. The
first part was conducted before the construction of the
planned development (sample x).
Primary data collection : Methodology
Time of day and date , recorded
traffic (in both directions) on 10 streets around the
development selected randomly)was accounted for 10
minutes. Stopwatch was being used for timing purpose and
a simple tally chart for recording the data.
The tally was filled at different times of the day.

4. For the second study (sample y), she waited until 2 months after the
development had been completed. She went to another 10 sites (selected
randomly) and repeated the test.
She then devised the following null hypothesis (H):
ₒ
‘There is no significant difference in traffic flows before and after the
development.’
Now let’s take a look at the formula:
U = N .N +
ₓ ₓ ᵧ
N(N + 1)
ₓ ₓ
2
- Σr
ₓ
U is the Mann
ₓ
Whitney
calculation for
sample x
n is the number in
the sample
Σr is the sum of
ₓ
ranks for sample x
(‘sum of’ just
means added
together)

5. The best way to proceed is to incorporate the findings into a table that also
allows you to calculate the result. When you get two or more equal values,
use the mean rank. Here are the student’s findings:
Total traffic
flow in 10
minutes (ₓ)
Rank
rₓ
Site Number Total traffic
flow in 10
minutes (ᵧ)
Rank
rᵧ
126 11 1 194
148 7 2 128
85 15.5 3 69
61 19 4 135
179 4 5 171
93 12.5 6 149
45 20 7 89
189 3 8 248 1
85 15.5 9 79
93 12.5 10 137

6. Σr = 120
ₓ
Σr =
ᵧ
Ranking puts values in order from highest to lowest.
Next, she substituted the data into the formula:
U = 10x10 +
ₓ
U = 100 +
ₓ
U = 100 + 55 – 120
ₓ
U = 35
ₓ
U = N .N +
ₓ ₓ ᵧ
N(N + 1)
ₓ ₓ
2
- Σr
ₓ
10(10 + 1)
2
- 120
110
2
- 120

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