Question

Are Southern and Western states equally prone to fatal lightning strikes? Suppose the number of lightning strike fatalities over a 5-year period for Southern and Western states are shown as follows.

Southern State	Fatalities
AL	5
AR	1
FL	17
GA	7
KY	5
LA	5
MS	4
NC	3
OK	2
SC	4
TN	0
TX	9
VA	0

Western State	Fatalities
AZ	6
CA	1
ID	2
MT	2
NM	2
NV	0
OR	2
UT	3
WA	0
WY	4

Use α = 0.05 and test to determine whether the distribution of lightning fatalities is the same for these two regions.

Find the value of the test statistic:

W = ?

Answer 1

Ho: the distribution of lightning fatalities is the same for these two regions

H1: the distribution of lightning fatalities is the not same for these two regions

wilxocon rank sum test

sample 1	sample 2	rank for sample 1	rank for sample 2
5	6	18	20
1	1	5.5	5.5
17	2	23	9
7	2	21	9
5	2	18	9
5	0	18
4	2	15	9
3	3	12.5	12.5
2	0	9
4	4	15	15
0
9		22
0

sample 1

sample size , n1 = 13

sum of ranks , R1 = 177

sample 2

sample size , n2 = 10

sum of ranks ,R2 = 89

W=sum of ranks for smaller sample size =89

value of the test statistic:

W =89