Three different brands of magnetron tubes (key components in microwave ovens) were stress tested and the number of hours each operated without repair was recorded (see table). Although these times do not represent typical service life times, they do indicate how well these tubes can withstand extreme stresses.

Prove that the mean duration with effort is the same for all three brands. What assumptions are necessary for the validity of this procedure?

Using a suitable test, determine if there is evidence to conclude that magnetron tube brands tend to differ in duration with stress using an of .05.

Using a programmed excel or minitab