A likelihood ratio test for the equality of proportions of two normal populations
In sampling inspection by variables, an item is considered defective if its quality characteristic Y falls below some specification limit L0. We consider switching to a new supplier if we can be sure that the proportion of defective items for the new supplier is smaller than the proportion defective for the present supplier. Assume that Y has a normal distribution. A test for comparing these proportions is developed. A simulation study of the performance of the test is presented.