Question

Karen wants to advertise how many chocolate chips are in each Big Chip cookie at her bakery. She randomly selects a sample of 48 cookies and finds that the number of chocolate chips per cookie in the sample has a mean of 15.2 and a standard deviation of 1.3. What is the 80% confidence interval for the number of chocolate chips per cookie for Big Chip cookies?

Enter your answers accurate to one decimal place (because the sample statistics are reported accurate to one decimal place).

Answer 1

We have given that,                  
                  
Sample mean =15.2          
Sample standard deviation =1.3      
Sample size =48          
Level of significance=1-0.80=0.2          
Degree of freedom =47          
                  
t critical value is (by using t table)=   1.3          
                  
Confidence interval formula is                   


=(14.9561 , 15.4439)              
                  
                  
Lower confidence limit=15.0      
                  
Upper confidence limit=15.4