In: Statistics and Probability
Test scores of 9 randomly selected students are: 83, 73, 62, 63, 71, 77, 59, 92,77 Compute the 99% confident interval of the true mean.
We have for given data,      
       
          
   
Sample mean =73      
Sample standard deviation =10.69  
Sample size =9      
Level of significance=   1-0.99=0.01  
   
Degree of freedom =8      
          
   
t critical value is (by using t table)=3.355  
   
          
   
Confidence interval formula is       
       
=(61.05,84.96)      
   
          
   
          
   
Lower confidence limit=61.05  
          
   
Upper confidence limit=   84.96