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Tae-Gweon JEONG,Bao-Feng PAN 한국항해항만학회 2014 한국항해항만학회지 Vol.38 No.6
The Korean government has introduced and enforced maritime traffic safety assessment to secure traffic safety since 2010. The maritime traffic safety assessment is needed by law to design a new port or modify an existing one. According to Korea Maritime Safety Act, in the assessment the propriety of marine traffic system consists of the safety of channel transit and berthing/unberthing maneuver, safety of mooring, and safety of marine traffic flow. The safety of channel transit and berthing/unberthing maneuver can be evaluated only by ship-handling simulation. The ship-handling simulation is carried out by sea pilots working with the port concerned. The vessel’s proximity measure is an important factor to evaluate traffic safety. The proximity measure is composed of vessel’s closest distance to channel boundary and probability of grounding/collision. What is more, the probability of grounding becomes important. According to central limit theorem, a sample has a normal distribution on condition that its size is more than 30. However, more than 30 simulation runs bring about the increase of assessment period and difficulty of employing sea pilots. Therefore this paper is to find out minimum sample size for evaluating vessel’s proximity. First sample sets of size of 3, 5, 7, 9 etc. are selected randomly on the basis of normal distribution. And then KS test for goodness of fit and t-test for confidence interval are applied to each sample set. Finally this paper decides the minimum sample size. As a result this paper suggests the minimum sample size of 5, that is, the simulation of more than five times.
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정태권,PAN BAOFENG 한국항해항만학회 2014 한국항해항만학회지 Vol.38 No.6
The Korean government has introduced and enforced maritime traffic safety assessment to secure traffic safety since 2010. The maritime traffic safety assessment is needed by law to design a new port or modify an existing one. According to Korea Maritime Safety Act, in the assessment the propriety of marine traffic system consists of the safety of channel transit and berthing/unberthing maneuver, safety of mooring, and safety of marine traffic flow. The safety of channel transit and berthing/unberthing maneuver can be evaluated only by ship-handling simulation. The ship-handling simulation is carried out by sea pilots working with the port concerned. The vessel’s proximity measure is an important factor to evaluate traffic safety. The proximity measure is composed of vessel’s closest distance to channel boundary and probability of grounding/collision. What is more, the probability of grounding becomes important. According to central limit theorem, a sample has a normal distribution on condition that its size is more than 30. However, more than 30 simulation runs bring about the increase of assessment period and difficulty of employing sea pilots. Therefore this paper is to find out minimum sample size for evaluating vessel’s proximity. First sample sets of size of 3, 5, 7, 9 etc. are selected randomly on the basis of normal distribution. And then KS test for goodness of fit and t-test for confidence interval are applied to each sample set. Finally this paper decides the minimum sample size. As a result this paper suggests the minimum sample size of 5, that is, the simulation of more than five times.
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수서곤충 군집분석에 있어서 최적표본크기의 결정 - 방태천 모형
윤일병,노태호,이성진,박재홍,배연재 한국생태학회 1998 Journal of Ecology and Environment Vol.21 No.5
A molel study was conducted to determine the optimal sample size for the analysis of the aquatic insect community in a stream reach of the Pangtae Creek, Kangwon-do in October 1995 and may 1996. The results showed that the required minimum sample size varied and depended on the purposes of the community analysis. Acoording to the Species: Area Curve method, at least 16 Surber samplings ($30{\times}30cm$) were required in a stream reach in each spring and fall survey. The species diversity index did not vary significantly as the sample size increased. Based on the coefficient of variation analysis, the minimum sample sizes of 10 were required in order to compare seasonal differences of the community in the study area. Considering the static community structure of aquatic insects, including both species numbers and individual numbers of aquatic insects, 11 and 7 samplings were optimal sizes for the fall and spring survey, respectively. We concluded that 12 Surber samplings from 3 riffle-pool sequences (4 samplings at each riffle-pool sequence) would be required in a stream reach (length 1 km) to obtain reliable as well as cost efficient data. Our model showed that the optimal sample size should be determined by interactions between minimum sample size, the degree of data reliability, and cost efficiency.
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김자영(Ja Young Kim),조영우(Young Woo Cho) 한국교육평가학회 2015 교육평가연구 Vol.28 No.3
혼합형 문항검사에서 양호한 동등화 결과를 얻기 위해 필요한 최소 표본크기에 대한 연구는 흔하지 않다. 본 연구는 동백분위 동등화 방법을 사용하여 검사의 길이, 서답형문항에 적용하는 점수 가중치, 그리고 문항유형 간에 상관관계를 고려하여 수용 가능한 동등화 결과를 도출하기 위해 필요한 최소 표본수를 추정하고자 한다. 서답형 문항에서의 점수 가중치와 문항유형 간의 상관관계는 최소 표본수를 결정하는데 큰 영향을 끼치지 않는 것으로 나타났다. 검사의 길이가 긴 경우, 선다형 문항으로만 이루어진 검사가 혼합형 문항검사보다 더 많은 표본수를 필요로 하는 것으로 나타났다. 그러나 검사의 길이가 짧은 경우, 혼합형 문항검사와 선다형 문항으로만 이루어진 검사에서 비슷한 표본수가 필요한 것으로 밝혀졌다. Very few studies have investigated the sample size requirements that lead to acceptable equating results with mixed-format tests. This study estimated a minimum sample size requirement considering test length, scoring weights on CR and correlation between multiple choice (MC) and constructed response (CR) item sections in the mixed-format tests using equipercentile equating method. Scoring weights and correlation between the two sections did not reveal any systematic difference in the sample size requirement. A larger sample size was required for the MC-only test than for the mixed-format test with the longer test while the sample size requirements were similar for the mixed format and MC-only tests with the shorter test.
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Aslam, Muhammad,Mughal, Abdur Razzaque,Hanif, Muhammad,Ahmad, Munir The Korean Statistical Society 2010 Communications for statistical applications and me Vol.17 No.5
Economic Reliability test plans(ERTP) are proposed considering that the life time of the submitted items follow the Pareto distribution of the second kind. For various specified acceptance number, sample size and producer's risk, a minimum test termination time is obtained. A comparison of proposed plan has been made with the existing plan developed by Aslam et al. (2010). The results are explained by tables and example.
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