Groton Boat Supply has received shipments of 15,000 pressurized cans of fiberglass sealant from each of its two main suppliers, Alcott Industries and Brookside, Inc. Inspectors at Groton take a simple random sample of 150 of the cans from the Alcott shipment and find that 15 are under pressurized. For a similar sample of 150 components from the Brookside shipment, nine of the cans are under pressurized. Construct and interpret the appropriate 95% confidence interval estimate of the overall difference in the proportion of under pressurized cans for the two shipments.