Producer's Risk Research Articles

Selection of conditional sampling plans for given AQL and LQL

This paper presents procedures and tables for the selection of conditional sampling plans, viz. conditional double sampling plan, chain-deferred sampling plan, link sampling plan, and ChSP-4A chain sampling plan for given acceptable quality level (AQL), producer's risk, limiting quality level and consumer's risk giving minimum sample size at AQL under the conditions of the Poisson model for the operating characteristic curve.

Selection of multiple deferred (dependent) state sampling plans for given acceptable quality level and limiting quality level

A table and a procedure are given for finding the multiple deferred (dependent) state sampling plans of type MDS-(c1, c2) involving minimum sum of producer's and consumer's risks for specified acceptable quality level and limiting quality level.

Selection of modified quick switching systems for given acceptable and limiting quality levels

A set of tables and procedures are given for finding the modified quick switching systems for which the sum of producer's and consumer's risks is minimized for specified acceptable quality level and limiting quality level.

Modified tables for the selection of qss–1 quick switching system for a given (aql,lql)

This paper presents a set of new tables and procedures for the selection of the following three types of Quick Switching (QS) systems for a given Acceptable Quality Level (AQL), Limiting Quality Level (LQL), producer's risk and consumer's risk. (1) A Single sampling QS system with equal sample sizes but with different acceptance numbers (2) A Single sampling QS system with two different sample sizes but with same acceptance number and (3) A QS systen with double sampling normal inspection and single sampling tightened inspection The third type of QS systen is the one newly presented in this paper. The tables provide unique plans for a given set of conditions as well as providing a smaller sample size or a smaller sum of Average Sample Numbers(ASN) at the AQL and LQL

Program for Item - By - Item Sequential Sampling by Attributes

ABSTRACf. This computet program, which is written in BASIC Language for an IBM-PC or compatible computer, generates solutions to sequential sampling problems. Given the acceptable quality level, the producer's risk, the lot tolerance fraction defective and the consumer's risk. the program produces all or one of the following: i ) Graphical representation of the plan (provided the computer has the color graphics capability). ii) Table of acceptance and rejection numbers. iii) Operational characteristic curve. iv) Average sample number curve. Furthermore, the program has a unique feature of calculating the values of probability of acceptance and average sample number for any value of proportion defective between acceptable quality level and lot tolerance fraction defective.

Modified tables for the selection of quick switching systems for values of the given acceptable quality level and limiting quality level

The paper presents modified tables derived from the work of Romboski and Soundararajan & Arumainayagam for the selection of quick switching systems of type QSS-2, QSS-3 and QSS-4 for given values of acceptable quality level, limiting quality level, producer's risk and consumer's risk. The plans selected from the tables will involve a smaller average sample number at the acceptable quality level.

Autoregressive processes applied to acceptance sampling by varlables

The effect of serial correlation on acceptance sampling plans by variables has been examined in this paper assuming the quality measurements follow an AR(p) process. The effect of serial correlation can be examined by comparing OC curves, sample size and producer's risks, ∝, with that of the independent case when the process standard deviation, σ, is known. When σ is unknown and for large n, sampling plans can be constructed using the central limit theorem. However, for σ unknown and for small n, there is no satisfactory method of obtaining sampling plans.

Robustness of exponential test plans to Weibull distributions

Abstract Sequential life testing procedures for the exponential distribution may be used when the underlying distribution is Weibull with a shape parameter not equal to one. In this paper, the robustness of these procedures with respect to the consumer's and producer's risk and expected number of failures has been investigated. A numerical example is also given to illustrate the discrepancies.

Selection of a tightened-normal-tightened system for given values of the acceptable quality level and limiting quality level

A table and a procedure are given to find the tightened-normal-tightened system involving the minimum sum of producer's and consumer's risks for a specified acceptable quality level and limiting quality level.

Selection of double sampling attributes plan for given acceptable quality level and limiting quality level

Tables and procedures are given for finding the double sampling plan, conditional double sampling plan, link sampling plan, ChSP-4 and ChSP-4A chain sampling plans involving minimum sum of producer's and consumer's risks for specified Acceptable Quality Level and Limiting Quality Level

Producer's and Consumer's Risk When Proportion Defective Is a Random Variable

ABSTRACTIn acceptance sampling, producer's and consumer's risk are traditionally based on assumed fixed values of p, the proportion of the lot which is defective. A more useful definition of producer's risk would be the probability of rejecting a lot in which the proportion defective falls within some range of acceptable values. Similarly, a more useful definition of consumer's risk would be the probability of accepting a lot in which the proportion defective falls within some range of unacceptable values. In this paper, we construct measures of these more useful definitions of risk by assuming that p follows either a uniform or triangular probability distribution. The proposed measure yields consumer's risk values, β', which are smaller than the traditionally computed values by a factor of up to twenty times. The proposed measure of producer's risk, α', gives values smaller than traditional values by a factor of two to four times. Decision makers who adopt the proposed measures may be able to reduce sample sizes substantially while maintaining given risk levels.

System-Based Component-Test Plans and Operating Characteristics: Binomial Data

Component-test plans are often designed by allocating system reliability among the system's components, then choosing individual component plans suitable for demonstrating achievcment of each component's reliability goal. This approach does not consider how much information relative to the system reliability goal is provided by the ensemble of component tests. We consider the notion of system reliability operating characteristic (OC) curves, based on the component tests, and illustrate their use in designing or evaluating an overall test program. By specifying OC values (akin to producer's and consumer's risks), optimum, system-ortented component-test plans can be derived. These ideas are illustrated for a series system, and for a simple series-parallel system, with binomial data.

System-Based Component-Test Plans and Operating Characteristics: Binomial Data

Component-test plans are often designed by allocating system reliability among the system's components, then choosing individual component plans suitable for demonstrating achievcment of each component's reliability goal. This approach does not consider how much information relative to the system reliability goal is provided by the ensemble of component tests. We consider the notion of system reliability operating characteristic (OC) curves, based on the component tests, and illustrate their use in designing or evaluating an overall test program. By specifying OC values (akin to producer's and consumer's risks), optimum, system-ortented component-test plans can be derived. These ideas are illustrated for a series system, and for a simple series-parallel system, with binomial data.

A note on the accuracy and precision of137Cs measurements in foodstuffs

Formulas for the precision and accuracy of137Cs measurements and of the consumer's and producer's risks in routine control are given. The limit of determination is determined by the combination of natural background, compton continuum of the sample aliquot, counting efficiency and the residual uncertainty in positioning.

Improvement of Concrete Strength Statistical Control

Abstract Extensive research is being carried out in the area of concrete strength statistical control. Acceptance control plans are improved to reduce consumer's and producer's risks: the producer's risk consists in rejecting good-quality concrete, while that of the consumer, in accepting a substandard concrete. ACI 318 provides a low-level risk for a producer and a high-level risk for a consumer. It is demonstrated that the consumer's risk substantially decreases with the introduction of the quality assurance system. The need to provide several acceptance criteria with various required probabilities of specified strength f′c and consumer's allowable risk in national codes is analyzed. In addition, two procedures are given: the first consists in taking into account the actual concrete strength distribution, and the second, in rejecting gross errors.

Finite difference analysis of reliability optimization through sampling techniques

This paper describes qualitative and quantitative techniques for reliability sampling plans based on failure density functions (MTTF, MTBF and MTTR) as expected values and as functions of time duration ( t ). Examples are provided of how the techniques are applied in determining plans for a specified lot size. These plans are to test service life, the effectiveness of reliability and MTTF, MTBF and MTTR as expected values and as functions of t and the percentage of reliable units expected in any lot size based on consumer's and producer's risks. Some graphs are constructed from which we can investigate the required aims. Several decision plans for several specified confidence limits, and variable percentages of deterioration of components, are shown for several sample sizes and specified lot sizes. The techniques used in this research, which are based on the calculus of finite differences, on statistical simulation and on the complex stochastic process for determining the relations required, are applicable to all statistical distributions, provided that the components are statistically independent.

Determination of single sampling attributes plans for given (aql. aoql)

This paper presents tables and a computer program for determining single sampling plans for given AQL, producer's risk and AOQL for the case of nonconforming units and nonconformities. Comparison with Soundararajan's (1981) procedures for selection of single sampling plans for given (AQL, AOQL) is also given

Aseptic integrity and microhole determination of packages by gas leakage detection

In principle, an aseptic package should protect against any type of microbe penetration. It means that each microhole must be less than about 0.5μm in diameter. In practice this critical limit may be much higher, owing to various factors, and consequently a controlling system does not necessarily have to have such a sensitivity. Controlling systems based on gas leakage detection have been suggested. In this report the basic validity range of such systems, including either mass spectrometer detection or an infra-red spectrometer, is analysed and various crucial factors are clarified as a basis for technical development. The actual control principle assumes that transmission of gases through the package originates only from microholes and cracks and that gas permeation through the packaging material is negligible. However, in practice the gas permeation may be considerable. For example, a package having a polyethylene (LDPE) barrier layer of 50μm in thickness has a gas permeation comparable to what is coming out through a pinhole of 10μm in diameter, and accordingly only much bigger microholes can be determined, with reference to calculations presented. If the barrier is improved by a Saran® layer (PVDC) of 25μm the gas permeation is still disturbing and only holes bigger than about 5μm in diameter may be detected. If instead the barrier is improved by an aluminium layer, gas permeation is negligible in most cases, and the basic principle of the gas leak detection systems is valid. Infra-red spectrometer based systems theoretically need at least a test time of 0.5 min and in practice much more to detect a microhole of 10μm in diameter-to collect a sufficient quantity of trace gas. Mass spectrometer based systems are in principle not testing time limited assuming a rapid enough vacuum pump can be arranged and that moisture interferences do not arise from the packaging material or from the packaged contents. Further, some aspects on the necessity of introduction a 100% control system, vis-a- vis a statistical control system, are given in terms of producer's and consumer's risks. About 100 packagings/h must be tested at ordinary production speed (1000–3000 packagingslh−1) to check accepted quality levels of 0.1% defectives. At higher quality levels, i.e. less than 0.1% defectives, the sample size needed increases rapidly towards 100% of the total production.

BEMARKINGSDOELTREFFENDHEID IN DIE AKWAKULTUURBEDRYF / Marketing efficiency in the aquaculture industry

Abstract Freshwater aquaculture is stimulated by a decline in the natural marine resources. Advanced progress has already been achieved in the technical research area, contrary to research in the economic and marketing areas which were neglected. It is an industry characterized by high risks, lack of structural organization and the absence of an effective marketing system. This research is aimed at addressing the institutional organization and marketing system problems of the industry. The objective is the provision of guidelines for the development of a efficient and effective marketing system. The analysis was based on surveys amongst freshwater aquaculture producers and distributors and surveys of the urban black and white consumers. An analysis of the sea fisheries industry was also done. Trout and barbell (catfish) are the most important commercial freshwater fish species. Producer's risks are increased by relative large capital investments needed and the unavailability of inputs. Most of the marketi...

A design for single sampling attribute plan based on fuzzy sets theory

Problems in the design of sampling inspection plans have been studied for a long time as an important subject in quality control. Especially, in the case of a single sampling attribute plan, one would like the producer's risk to equal α and the consumer's risk to equal β exactly, but this is usually not possible since the sample size n and the acceptance number c must be integers. In this paper a new design procedure for the single sampling attribute plan based on fuzzy sets theory is presented by means of formulating this problem as a fuzzy mathematical programming one.