Question: Suppose that the radios in the 1,000 containers of problem were produced in five different factories, each factory known to have different internal production controls. Each container is marked with a number denoting the factory where the radios were made. Suggest an appropriate sampling method in this case, and discuss its advantages.
Problem: A quality control sampling scheme was carried out by Sony for estimating the percentage of defective radios in a large shipment of 1,000 containers with 100 radios in each container. Twelve containers were chosen at random, and every radio in them was checked. The numbers of defective radios in each of the containers are 8, 10, 4, 3, 11, 6, 9, 10, 2, 7, 6, 12. Give a 95% confidence interval for the proportion of defective radios in the entire shipment.