Question

Aisha wants to advertise how many chocolate chips are in each Big Chip cookie at her bakery. She randomly selects a sample of 71 cookies and finds that the number of chocolate chips per cookie in the sample has a mean of 14.2 and a standard deviation of 3.3. What is the 98% confidence interval for the number of chocolate chips per cookie for Big Chip cookies? Assume the data is from a normally distributed population. Round answers to 3 decimal places where possible.

Answer 1

We have given that,          
          
Sample mean =14.2  
Sample standard deviation =3.3
Sample size =71  
Level of significance=1-0.98=0.02  
Degree of freedom =70  
          
t critical value is (by using t table)=   2.381
          
Confidence interval formula is   


=(13.268,15.132)      
          
          
          
Lower confidence limit=   13.268  
          
Upper confidence limit=   15.132