We deal with sampling by variables with two-way protection in the case of a N(μ,σ2)\documentclass[12pt]{minimal}
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\begin{document}$$N\>(\mu ,\sigma ^2)$$\end{document} distributed characteristic with unknown σ\documentclass[12pt]{minimal}
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\begin{document}$$\sigma $$\end{document}. The LR sampling plan proposed by Lieberman and Resnikoff (JASA 50: 457-\documentclass[12pt]{minimal}
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\begin{document}$${-}$$\end{document}516, 1955) and the BSK sampling plan proposed by Bruhn-Suhr and Krumbholz (Stat. Papers 31: 195–207, 1990) are based on the UMVU and the plug-in estimator, respectively. For given p1\documentclass[12pt]{minimal}
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\begin{document}$$p_1$$\end{document} (AQL), p2\documentclass[12pt]{minimal}
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\begin{document}$$p_2$$\end{document} (RQL) and α,β\documentclass[12pt]{minimal}
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\begin{document}$$\alpha ,\beta $$\end{document} (type I and II errors) we present an algorithm allowing to determine the optimal LR and BSK plans having minimal sample size among all plans satisfying the corresponding two-point condition on the OC. An R (R: A language and environment for statistical computing, R Foundation for Statistical Computing, Vienna, Austria. ISBN 3-900051-07-0, URL http://www.R-project.org/2012) package, ExLiebeRes‘ (Krumbholz and Steuer ExLiebeRes: calculating exact LR- and BSK-plans, R-package version 0.9.9. http://exlieberes.r-forge.r-project.org2012) implementing that algorithm is provided to the public.