A single test on a certain device costs more than the entire lot. It is therefore decreed that not more than three tests will be performed per lot. The following acceptance plan will therefore be employed: Test two units. If both function accept the lot. If both fail, reject the lot. Otherwise test another item. If it fails, reject the lot. If it functions accept.

i) Assuming the binomial distribution is applicable, write down the expression for the OC curve, i.e., write the expression for the probability of acceptance as a function of the lot fraction defective p. Evaluate it at lot fraction defective of p=2%.

ii) Write the expression for the OC curve of a single sampling plan having n=3 and c=1. Evaluate it when p=2%

iii) For the first plan the sample size is a random variable assuming the value n=2 or n=3. Compute the average sample size when the lot is 2% defective.