95% confidence interval for  is  =(15.16 , 16.84)
Example 4 (Exercise 9.18):
Sample sizes are small and population variances are unknown. . Notice that this is a two-tailed test.
Test statistics:  =6.166
Decision:
(i) Reject H0 if t -t/2;v= -2.447 or t t/2;v =2.447 where =0.05 and v=6.886. t =6.166 > 2.447 and reject H0.
(ii) P-value = 2P(t>6.166)=2(0)=0. Since the P-value =0.05, reject H0.
Conclusion: the true average densities for two different types of brick are different.
Share with your friends: | 
