The feeding habits of two species of net-casting spiders are studied. These species, the Dinopis and Menneus, coexist in eastern Australia. One variable of interest is the size of the prey of each species. Is there a difference in average prey size between Dinopis and Menneus based on the data below? Dinopis prey size (mm) Menneus prey size (mm) 12.9 11.9 10.2 5.3 10.2 7.1 6.9 7.5 7.4 9.9 10.9 10.3 7.0 14.4 11.0 9.2 10.5 11.3 10.1 8.8 Test of equality of variances: Ho: Ha: Test statistic & value: p-value: Statistical conclusion: Test of means: Ho: Ha: Test statistic & value: p-value: Statistical conclusion: Practical conclusion: Dinopis prey size (mm) Menneus prey size (mm) 12.9 11.9 10.2 5.3 10.2 7.1 6.9 7.5 7.4 9.9 10.9 10.3 7.0 14.4 11.0 9.2 10.5 11.3 10.1 8.8 Solution sample size,n sample mean,x standard deviation,s alpha,a = 0.05 n1= 10 , x1= 10.26 , s1= 2.5136 n2= 10 , x2= 9.02 , s2= 1.8967 -------------------------------------------------------------------------------------------------------------------- Test of equality of variances: H0: S1^2 = S1^2 (equal population variance) H1: S1^2 is not equal to S1^2 test statistic, F = s1^2 / s2^2 test statistic, F = 1.756 degree of freedom,df = n1-1,n2-1 = 9,9 P-value = 0.207 Statistical conclusion: since P-value>0.05 hence we fail to reject H0 Practical conclusion:so we conclude that population variances are equal -------------------------------------------------------------------------------------------------------------------- Test of means: H0: u1 = u2 Ha: u1 is not equal to u2 standard error, SE = sqrt((s1^2/n1)+(s2^2/n2) SE = 0.99577 test statistic, t = (x1-x2) / SE test statistic, t = 1.245 degree of freedom,df = n1+n2-2 = 18 P-value = 0.23 Statistical conclusion: since P-value>0.05 hence we fail to reject H0 Practical conclusion:so we conclude that there is NO difference in average prey size between Dinopis and Menneus.

1. The feeding habits of two species of net-casting spiders are studied. These species, the Dinopis
and Menneus, coexist in eastern Australia. One variable of interest is the size of the prey of each
species. Is there a difference in average prey size between Dinopis and Menneus based on the
data below?
Dinopis prey size (mm)
Menneus prey size (mm)
12.9
11.9
10.2
5.3
10.2
7.1
6.9
7.5
7.4
9.9
10.9
10.3
7.0
14.4
11.0
9.2
10.5
11.3
10.1
8.8

2. Test of equality of variances:
Ho:
Ha:
Test statistic & value:
p-value:
Statistical conclusion:
Test of means:
Ho:
Ha:
Test statistic & value:
p-value:
Statistical conclusion:
Practical conclusion:
Dinopis prey size (mm)
Menneus prey size (mm)
12.9
11.9

3. 10.2
5.3
10.2
7.1
6.9
7.5
7.4
9.9
10.9
10.3
7.0
14.4
11.0
9.2
10.5
11.3
10.1
8.8
Solution
sample size,n
sample mean,x
standard deviation,s
alpha,a = 0.05
n1= 10 , x1= 10.26 , s1= 2.5136
n2= 10 , x2= 9.02 , s2= 1.8967
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Test of equality of variances:

4. H0: S1^2 = S1^2 (equal population variance)
H1: S1^2 is not equal to S1^2
test statistic, F = s1^2 / s2^2
test statistic, F = 1.756
degree of freedom,df = n1-1,n2-1 = 9,9
P-value = 0.207
Statistical conclusion: since P-value>0.05 hence we fail to reject H0
Practical conclusion:so we conclude that population variances are equal
--------------------------------------------------------------------------------------------------------------------
Test of means:
H0: u1 = u2
Ha: u1 is not equal to u2
standard error, SE = sqrt((s1^2/n1)+(s2^2/n2)
SE = 0.99577
test statistic, t = (x1-x2) / SE
test statistic, t = 1.245
degree of freedom,df = n1+n2-2 = 18
P-value = 0.23

5. Statistical conclusion: since P-value>0.05 hence we fail to reject H0
Practical conclusion:so we conclude that there is NO difference in average prey size between
Dinopis and Menneus