The triggering device for an automobile airbag restraint is required to have a reliabil-ity of 95 per cent when tested on an impact test rig. This reliability is to be established at 90 per cent confidence. The test is destructive. For a series of tests on a specific design, failures occurred on the 11th, 43rd, 49th, 75th, 102nd and 144th samples. All other samples passed. The 160th sample has just been tested.
(a) Plot the results on suitable binomial plotting paper (Chartwell 5703, or suitable TEAM paper, as described in the text) and estimate the current reliability and its 90 per cent lower confidence limit. Hence decide if the test requirements have been met. If not, estimate the amount of further testing required if there is no improvement to the device.
(b) Consider whether doing the further testing indicated in (a) is sensible.