  ASN-Minimax double sampling plans by variables for a normally distributed
quality characteristic with unknown standard deviation and two-sided
specification limits are introduced. These plans base on the essentially
Maximum-Likelihood (ML) estimator p* and the Minimum Variance Unbiased (MVU)
estimator ^p of the fraction defective p. The operation characteristic (OC) of
the ASN-Minimax double sampling plans is determined by using the independent
random variables p*_1, p*_2 and ^p_1, ^p_2, which relate to the first and
second samples, respectively. The maximum of the average sample number (ASN) of
these plans is shown to be considerably smaller than the sample size of the
corresponding single sampling plans.
