During Summer 2013, American Airlines introduced a new method for passengers to board a narrowbody aircraft. The new procedure affected passengers traveling light, those carrying one item that fits...

During Summer 2013, American Airlines introduced a new method for passengers to board a narrowbody aircraft. The new procedure affected passengers traveling light, those carrying one item that fits under the seat. The system was designed to decrease the total boarding time, and improve on-time performance. Independent random samples of American and US Airways flights were obtained and the boarding time (in minutes) for each was recorded. The summary statistics are given in the following table

Is there any evidence to suggest that the new boarding procedure has decreased the population mean boarding time? Useand assume the populations are normal with equal variances.

A recent study was conducted to determine the curing efficiency (time to harden) of dental composites (resins for the restoration of damaged teeth) using two different types of lights. Independent random samples of lights were obtained and a certain composite was cured for 40 seconds. The depth of each cure (in mm) was measured using a penetrometer. The summary statistics for the Halogen light