Question

4. The production manager for the XYZ manufacturing company is concerned that the customer orders are being shipped late. He asked one of his planners to check the timeliness of shipments for 1000 orders. The planner randomly selected 1000 orders and found that 120 orders were shipped late. Construct the 90% confidence interval for the proportion of orders shipped late.

Answer 1

We have given,              
              
x=120          
n=1000          
Estimate for sample proportion
Level of significance is =1-0.90=0.1      
Z critical value(using Z table)=1.645  
  
Confidence interval formula is              


=(0.1031,0.1369)              
Lower limit for confidence interval=0.1031  
              
Upper limit for confidence interval=0.1369