Stichprobenpläne

Stichprobenpläne, also known as sampling plans, are statistical tools used in quality control and quality assurance. They define a specific procedure for inspecting a subset of items from a larger batch or lot to make a decision about the quality of the entire lot. The primary goal is to determine whether the lot meets a predetermined quality standard, such as an acceptable quality level (AQL), with a certain level of confidence.

The design of a Stichprobenplan involves several key parameters. These include the lot size, the sampling method, the inspection level, and the acceptance and rejection criteria. The sampling method specifies how the sample is drawn from the lot, which can be random, systematic, or stratified. The inspection level determines the rigor of the inspection, often relating the sample size to the lot size.

The acceptance and rejection criteria are based on the number of nonconforming items found in the sample. If the number of defects in the sample is below a specified acceptance number, the lot is accepted. If it exceeds a rejection number, the lot is rejected. Stichprobenpläne are designed to balance the risk of accepting a defective lot (producer's risk) with the risk of rejecting a good lot (consumer's risk).

Common types of Stichprobenpläne include single sampling, double sampling, and multiple sampling plans. Single sampling involves one sample inspection. Double sampling allows for a second sample if the results of the first are inconclusive. Multiple sampling extends this to several samples. These plans are widely used in manufacturing, auditing, and various other fields where it is impractical or too costly to inspect every single item.