Unverfälschte Variablenprüfpläne für exponentialverteilte Merkmale mit zweiseitigen Toleranzgrenzen

As a well known fact the standard X²-procedures (e.g. confidence intervals for σ², tests of the hypothesis H:″σ=σ_o″ in the case of normal population with variance σ²) are biased. We refer to some useful tables which enable in the case of normal population to procure unbiased confidence intervals or confidence intervals with minimal length for σ², control charts for σ with minimal distance between the limit lines, and unbiased tests of H:″σ=σ_o″. Another important application yields—as main result of the present paper—unbiased sampling plans in the case of an exponential distributed attribute with upper and lower specification limit (two-way-protection). It turns out to be possible, also in the case of exponential distribution, to reduce the sample size by using incomplete prior information about the proportion p of defectives.