A study of nonfatal occupational injuries in the United States found that about 31% of all injuries

A study of nonfatal occupational injuries in the United States found that about 31% of all injuries in the service sector involved the back. The National Institute for Occupational Safety and Health (NIOSH) recommended conducting a comprehensive ergonomics assessment of jobs and workstations. In response to this information, Mark Glassmeyer developed a unique ergonomic handcart to help field service engineers be more productive and also to reduce back injuries from lifting parts and equipment during service calls. Using a sample of 382 field service engineers who were provided with these carts, Mark collected the following data:

Year 1(without cart)
Year 2(with cart)

Average call time

8.27 hours
7.98 hours

Standart Deviation call time

1.36 hours
1.21 hours

Proportion of back injuries

0.018
0.01

Find 95% confidence intervals for the average call times and back injuries in each year. What conclusions would you reach based on your results?