Method of determining at least one tolerance band limit value for a technical variable under test and corresponding calculation device

A method executable by a computing system, the method comprising:

• calculating by a processor a plurality of sample tolerance band limit values using a sample-specific conditional probability distribution function which is a function of sample values of a sample;
• obtaining by the processor at least one tolerance band limit value from the sample tolerance band limit values of different samples,
• wherein the samples comprise values of a technical variable under test of the associated sample,
• wherein the at least one tolerance band limit value is obtained using a location measure of a distribution according to which the sample tolerance band limit values are distributed,
• wherein the technical variable under test is distributed according to an underlying extreme value distribution function,
• wherein the technical variable relates to a physical characteristic of a product that is producible in an industrial mass production process, and
• using the at least one tolerance band limit value to calculate at least one of an upper specification level or a lower specification level for monitoring the industrial mass production process;
• wherein a) the product is an autoinjector for automatic drug injection comprising a spring member that generates an injection force and wherein the variable under test is a cap removal force of a cap of the autoinjector, a cap placement force of the cap of the autoinjector, or a breakage force of the autoinjector, or
• wherein b) the product is a multi dose pen injection device and wherein the variable under test is a dial torque for dialing the dose of the multi dose pen, a cap removal force of a cap of the multi dose pen, a cap placement force of the cap of the multi dose pen, or a breakage force of the multi dose pen;
• the method further comprising:
• testing whether a chosen sample size of the samples is great enough using the location measure of the tolerance band limit values, and
• if the chosen sample size is not great enough, increasing the chosen sample size and generating new samples that have an increased sample size and performing the obtaining step again, or
• if the chosen sample size is great enough, using the chosen sample size for defining a sampling plan or using the chosen sample size to calculate an improved value of the sample size for a sampling plan;
• wherein the method further comprises:
• producing a lot of the products;
• taking a sample group of products from the lot according to the sample size specified in the sampling plan;
• determining the values of the variable under test for each product of the sample group;
• comparing the values with a tolerance interval that is calculated using the tolerance band limit value according to the sampling plan;
• and
• deciding whether to accept the lot or to reject the lot based on results of the comparison.