Question

An article gave the following summary data on shear strength (kip) for a sample of 3/8-in. anchor bolts: n = 71, x = 4.50, s = 1.40. Calculate a lower confidence bound using a confidence level of 90% for true average shear strength. (Round your answer to two decimal places.)

Answer 1

We have given that,          
          
Sample mean =4.5  
Sample standard deviation =1.4
Sample size =71  
Level of significance=1-0.90=0.1  
Degree of freedom =70  
          
t critical value is (by using t table)=   1.667  
          
a lower confidence bound formula


=4.22