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The systematic sampling for inferring the survey indices of Korean groundfish stocks
( Saang-yoon Hyun ),( Young Il Seo ) 한국수산과학회(구 한국수산학회) 2018 Fisheries and Aquatic Sciences Vol.21 No.3
The Korean bottom trawl survey has been deployed on a regular basis for about the last decade as part of groundfish stock assessments. The regularity indicates that they sample groundfish once per grid cell whose sides are half of one latitude and that of one longitude, respectively, and whose inside is furthermore divided into nine nested grids. Unless they have a special reason (e.g., running into a rocky bottom), their sample location is at the center grid of the nine nested grids. Given data collected by the survey, we intended to show how to appropriately estimate not only the survey index of a fish stock but also its uncertainty. For the regularity reason, we applied the systematic sampling theory for the above purposes and compared its results with a reference, which was based on the simple random sampling. When using the survey data about 11 fish stocks, collected by the spring and fall surveys in 2014, the survey indices of those stocks estimated under the systematic sampling were overall more precise than those under the simple random sampling. In estimates of the survey indices in number, the standard errors of those estimates under the systematic sampling were reduced from those under the simple random sampling by 0.23~27.44%, while in estimates of the survey indices in weight, they decreased by 0.04~31.97%. In bias of the estimates, the systematic sampling was the same as the simple random sampling. Our paper is first in formally showing how to apply the systematic sampling theory to the actual data collected by the Korean bottom trawl surveys.
Estimates of Korea`s bilateral export functions
( Saang Joon Baak ) 서강대학교 시장경제연구소(구 서강대학교 경제연구소) 2015 시장경제연구 Vol.44 No.1
This paper estimates bilateral export functions of Korea to its four major trading partners(China, the Euro Zone, Japan, and the US) with the data from 2000Q1 to 2014Q1 and examines the impacts of changes in the global economic environment on Korean exports based on the estimation results. Both income elasticity and price elasticity are estimated to have the expected signs. External demand for the products of Korea’s Asian trading partners also plays an important role in determining Korean exports to those countries. Although the recovery of the global economy is expected to contribute to an increase in Korean exports, appreciation of the Korean won will reduce its impact.
The systematic sampling for inferring the survey indices of Korean groundfish stocks
HYUN SAANG YOON,이성일 한국수산과학회 2018 Fisheries and Aquatic Sciences Vol.21 No.3
The Korean bottom trawl survey has been deployed on a regular basis for about the last decade as part of groundfish stock assessments. The regularity indicates that they sample groundfish once per grid cell whose sides are half of one latitude and that of one longitude, respectively, and whose inside is furthermore divided into nine nested grids. Unless they have a special reason (e.g., running into a rocky bottom), their sample location is at the center grid of the nine nested grids. Given data collected by the survey, we intended to show how to appropriately estimate not only the survey index of a fish stock but also its uncertainty. For the regularity reason, we applied the systematic sampling theory for the above purposes and compared its results with a reference, which was based on the simple random sampling. When using the survey data about 11 fish stocks, collected by the spring and fall surveys in 2014, the survey indices of those stocks estimated under the systematic sampling were overall more precise than those under the simple random sampling. In estimates of the survey indices in number, the standard errors of those estimates under the systematic sampling were reduced from those under the simple random sampling by 0.23~27.44%, while in estimates of the survey indices in weight, they decreased by 0.04~31.97%. In bias of the estimates, the systematic sampling was the same as the simple random sampling. Our paper is first in formally showing how to apply the systematic sampling theory to the actual data collected by the Korean bottom trawl surveys.