Reliability of Aircraft Radios The mean time between failures (in hours) for a Telektronic Company radio used in light aircraft is 420 h. After 15 new radios were modified in an attempt to improve reliability, tests were conducted to measure the times between failures. When Minitab is used to test the claim that the modified radios have a mean greater than 420 h, the results are as shown here. Does it appear that the modifications improved reliability?

Test of mu 5 420 vs mu . 420 Variable N Mean StDev SE Mean Time 15 442.2 44.0 11.4 Variable 95.0% Lower Bound T P Time 422.2 1.95 0.035