Consider the following statements in respect of double sampling plan:
1. Average number of pieces inspected is double that of single sampling.
2. Average number of pieces inspected is less than that for single sampling.
3. Decision to accept or reject the lot is taken only after the inspection of both samples.
4. Decision to accept or reject the lot is reached sometimes after one sample and sometimes after two samples.
Which of these statements are correct?
(a) 1, 2 and 3 (b) 2 and 4
(c) 1 and 4 (d) 2 and 3