Two different types of electrical cable insulation have recently been tested to determine the voltage level at which failures tend to occur. When specimens were subjected to an increasing voltage stress in a laboratory experiment, failures for the two types of cable insulation occurred at the following voltages:

Suppose that it is known that the amount of voltage that cables having type A insulation can withstand is normally distributed with unknown mean μA and known variance σ2 A = 40, whereas the corresponding distribution for type B insulation is normal with unknown mean μB and known variance σ2 B = 100. Determine a 95 percent confidence interval for μA − μB. Determine a value that we can assert, with 95 percent confidence, exceeds μA − μB.

Transcribed Image Text:

Type A 36 54 52 Type B 60 44 52 64 44 41 37 38 48 53 51 68 46 38 44 66 70 36 35 52 62 34 44