• 품질경영학회지
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• 제22권4호
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• pp.102-110
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• 1994

We investigate the small-sample behavior of the probability of rejection curves and its performance for a equivalence testing procedure based on confidence intervals which was developed with a motivation from bioequivalence studies. This type of equivalence studies are conducted frequently in pharmaceutical industries to compare the relative bioavailabilty of two formulations of a drug and can be applied various fields where assurance of quality equivalence is needed. From the Monte-Carlo simulation results we suggest proper sample sizes for the equivalence testing procedure.

• 산업경영시스템학회지
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• 제45권4호
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• pp.53-60
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• 2022

In a group-testing method, instead of testing a sample, for example, blood individually, a batch of samples are pooled and tested simultaneously. If the pooled test is positive (or defective), each sample is tested individually. However, if negative (or good), the test is terminated at one pooled test because all samples in the batch are negative. This paper considers a queueing system with a two-stage group-testing policy. Samples arrive at the system according to a Poisson process. The system has a single server which starts a two-stage group test in a batch whenever the number of samples in the system reaches exactly a predetermined size. In the first stage, samples are pooled and tested simultaneously. If the pooled test is negative, the test is terminated. However, if positive, the samples are divided into two equally sized subgroups and each subgroup is applied to a group test in the second stage, respectively. The server performs pooled tests and individual tests sequentially. The testing time of a sample and a batch follow general distributions, respectively. In this paper, we derive the steady-state probability generating function of the system size at an arbitrary time, applying a bulk queuing model. In addition, we present queuing performance metrics such as the offered load, output rate, allowable input rate, and mean waiting time. In numerical examples with various prevalence rates, we show that the second-stage group-testing system can be more efficient than a one-stage group-testing system or an individual-testing system in terms of the allowable input rates and the waiting time. The two-stage group-testing system considered in this paper is very simple, so it is expected to be applicable in the field of COVID-19.

• 산업경영시스템학회지
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• 제4권5호
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• pp.11-14
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• 1981

This study intends to decide the economic sample size based on the cost of sampling Inspection for destructive testing. The marginal percent defective is used as the lot tolerance percent defective (LTPD), and the Newton's iterative method is adopted to calculate the optimum sample size(n), given by the consumer's risk($\beta$ - risk) and the acceptance number(c).

• 한국임상수의학회지
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• 제27권4호
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• pp.421-426
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• 2010

In view of free from bluetongue (BT) in the domestic cattle population in Korea, the key of quarantine testing for BT virus (BTV) infection is detection of cattle previously exposed to the virus. The objective of this study was to estimate the probability of detecting a cattle infected with BTV using a stochastic modeling analysis of existing quarantine testing data. Three testing scenarios were considered in this study: serological testing of all animals in all imported lots (scenario 1), serological testing of a sample of cattle from all imported lots (scenario 2), and serological testing of 50% of imported lots (scenario 3). In scenario 2 and 3, it was assumed that cattle were sampled (sample size) within each lot to detect 5% of the cattle in each lot with a 95% confidence, taking into account diagnostic sensitivity of the ELISA (enzyme-linked immunosorbent assay). The model output was the total number of BTV-infected cattle and the prevalence of BTV infection in imported cattle from the US, Australia, Canada and Japan. Compared to the scenario 1, the probability of detecting a BTV-infected cattle was estimated to be 19% and 1.6% in scenario 2 and 3, respectively. Furthermore, the analyses showed a 95% confidence that BTV prevalence was less or equal to $9.7{\times}10^{-4}$ (median = $1.5{\times}10^{-5}$), indicating that, for the scenario 2 and 3 with serological testing for a sample of cattle, the risk of introducing an exotic strain of BTV into Korea through the importation of live cattle would not be acceptable.

• 한국축산식품학회지
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• 제34권6호
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• pp.852-857
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• 2014

This study was carried out to develop a simple, convenient, and reproducible testing device to determine wettability and dispersibility of dairy powders. The testing device consists of a sieve ($150{\mu}m$) attached to a sample chamber, sensors mounted on a supporting body and a main control unit containing a display panel. The sensors detect the difference in electrical resistance between air and water. A timer is automatically triggered by the sensor when the bottom of sample-loaded chamber contacts water in the petri dish. Wettability and dispersibility of commercial skim milk powders (SMPs) produced at different heating strengths (low-, medium-, and high-heat SMP) are compared using the new testing device. Wettability of the SMPs were correlated with particle size and are found to increase in the order of medium-, low-, and high-heat SMP regardless of the amount of sample tested. Dispersibility of SMPs showed the same trend and high heat-SMP which has the smallest particle size resulted in the lowest dispersibility. Unlike existing methods, the new testing device can determine both wettability and dispersibility of powders and successfully detected differences among the samples.

• 한국물환경학회지
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• 제29권4호
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• pp.568-573
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• 2013

In this study, we conducted whole effluent toxicity (WET) proficiency testing based on the results which $EC_{50}$ value of 3 types (A, B, C) unknown samples calculated from 32 water quality measurement agencies in Korea. WET proficiency testing was expected to their improve of analysis skill and ensure reliability of analysis results. Ultimately, it is intended to promote the reliable enforcement of WET. WET proficiency testing was evaluated using the z-score, robust z-score and the results showed that 30 participating agencies were "compliance". In addition, $EC_{50}$ values of "unknown sample A" were the normal distribution. Therefore, "unknown sample A" was considered as the most suitable standard toxicity substance.

• 한국건축시공학회지
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• 제8권4호
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• pp.105-114
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• 2008

This study investigates the saturation level of surface dryness, quantity of adhesive mortar, and the alien substance content of recycled aggregates for concrete to develop an adequate quality testing method for understanding the properties of recycled aggregates, which differ greatly from preexisting aggregates. For tests that measure the saturation level of surface dryness, where detail methods are applied differently according to the tester, various testing methods from across world were compared and analyzed. This study revealed that when measuring the saturation level of surface dryness of a certain sample, aggregates must be supplemented immediately whenever the height of the sample becomes lower than the measuring mold, and allowing the tamper to free fall on the sample will provide the most accurate results. When measuring the quantity of adhesive mortar of recycled aggregates for concrete, an acid solution was used, and since the quantity of adhesive mortar increases as the particle sizes gets smaller, the sample for testing should represent the entire granularity. Sulfuric acid solution is adequate for immersion, and the concentration should be 20% for best results. According to the alien substance content measurement, which was examined by the naked eye, the error range caused by the difference in particle size was neglectable, and therefore the sample should be $2.5{\sim}5.0mm$ in size concerning the accuracy and measuring time. Also, for coarse recycled aggregates, the sample should amount to 1kg for measuring alien substance content by the naked eye, which proves that assortment by the naked eye is the most adequate method for measuring the alien substance content of a recycled aggregate.

• Journal of the Korean Statistical Society
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• 제23권1호
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• pp.199-206
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• 1994

Sometimes a researcher with a view of conventional significance testing rejects his/her hypothesis, even through it could have not been rejected with a smaller sample. This can be a logical dilemma for a researcher who wants to "prove" a hypothesis rather than to show discrepancy from a null hypothesis. In this study, a new testing paradigm called equivalence testing via confidence interval will be developed so that it is suitable for the purpose of statistical proof.cal proof.

• Applied Biological Chemistry
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• 제32권4호
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• pp.357-361
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• 1989

두유 제조에서 얻어지는 두유박으로 밀가루 고오지를 이용하여 밀된장을 만든 결과 된장 숙성 중 환원당은 모든 시험구가 숙성 50일경까지 증가하다가 그 이후에는 감소하였고 두유박의 배합비가 많을수록 환원당의 함량이 감소하였으며 amino태 질소함량은 각 시험구 다같이 50일까지는 급격히 증가하나 그 이후에는 증가가 둔화되며 시험구별로는 숙성 초기에는 두유박의 배합비가 많을수록 amino태 질소 함량이 높았으나 숙성후기에는 두유박의 배합비가 많을수록 amino태 질소 함량이 낮았다. 총산 함량은 40일까지는 현저하게 증가하나 그 이후에는 둔화되었으며 각 시험구별로는 그 차이가 극히 적었다. 80일 숙성 된장의 색도는 두유박의 배합비가 많을수록 명도가 높으며 적색도가 약해지는 반면 황색도가 높게 나타났다. 숙성 90일 되는 된장의 관능 검사결과 콩나물 된장국은 대조구가 가장 좋고 두유박의 배합비가 많을수록 맛은 약간 떨어지나 대조구와 시험구 D 사이에만 유의차가 있을 뿐, 대조구와 시험구 A,B,C 사이에는 유의차가 없었다. 된장 그대로의 관능 검사 결과 대조구가 가장 좋은 점수를 얻었고, 대조구 A,B,C,D 순으로 낮은 점수를 얻어 두유박의 배합비가 많을수록 맛이 떨어지는 것으로 나타났으나 대조구와 시험구 A 사이, 시험구 B와 C 사이에는 유의차가 없었다.

• 한국전문물리치료학회지
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• 제19권3호
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• pp.124-131
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• 2012

Most conventional instruments measuring disability rely on total score by simply adding individual item responses, which is dependent on the items chosen to represent the underlying construct (test-dependent) and a test statistic, such as coefficient alpha for the estimate of reliability, varying from sample to sample (sample-dependent). By contrast, item response theory (IRT) method focuses on the psychometric properties of the test items instead of the instrument as a whole. By estimating probability that a respondent will select a particular rating for an item, item difficulty and person ability (or disability) can be placed on same linear continuum. These estimates are invariant regardless of the item used (test-free measurement) and the ability of sample applied (sample-free measurement). These advantages of IRT allow the creation of invariantly calibrated large item banks that precisely discriminate the disability levels of individuals. Computer adaptive testing (CAT) method often requiring a testing algorithm promise a means for administering items in a way that is both efficient and precise. This method permits selectively administering items that are closely matched to the ability level of individuals (measurement precision) and measuring the ability without the loss of precision provided by the full item bank (measurement efficiency). These measurement properties can reasonably be achieved using IRT and CAT method. This article aims to investigate comprehensive overview of the existing disability instrument for back pain and to inform physical therapists of an alternative innovative way overcoming the shortcomings of conventional disability instruments. An understanding of IRT and CAT method will equip physical therapist with skills in interpreting the measurement properties of disability instruments developed using the methods.