Two companies manufacture iron plates. In a sample of 800 plates taken from Manu

Question

Two companies manufacture iron plates. In a sample of 800 plates taken from Manufacturer 1, 720 met specification of tensile strength. In a sample of 600 plates taken from Manufacturer 2, 580 met the specification. Plates from Manufacturer 2 is more expensive, so it is decided that plates from Manufacturer 1 will be used unless it can be convincingly shown that Manufacturer 2 produces a larger proportion of plates meeting strength specification.
a)Test to determine which machine should be used. Use a=0.05.
b)Find a 95% confidence interval for the difference between the proportions of plates meeting specifications produced by the two Manufacturers.
c)Check the assumptions of the procedures.

Explanation / Answer

proportion nonconforming for the sample from manufacturer1 = 80/800 = p1 = 0.1 proportion nonconforming for the sample from manufacturer2 = 20/600 = p2 = 0.033 so, obviously, manufacturer2's plates are better. also, acceptance limit is 0.05, and p2

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