• Survey Research
• /
• v.5 no.1
• /
• pp.93-101
• /
• 2004

In business survey, cut-off sampling is usual, The contribution from cut-off part of the population is at least small in comparison with the remaining population. In this case, part of the target population is excluded from the selection and parameter estimations are only based on Take-all and Take-some stratum. It may be tempting not to use resources on enterprises that contribute little to the overall results of the survey. And this reduces the response burden for these small enterprises. But, the size of cut-off stratum has been increased as a way to manage reduced budgets. This leads to additional bias. In this study, the population have been separated as three stratum, cut -off, take-some, take-all, and we will estimate cut-off part using auxiliary variable.

• The Korean Journal of Applied Statistics
• /
• v.33 no.4
• /
• pp.409-420
• /
• 2020

In business survey, modified cut-off sampling is commonly used to greatly increase the accuracy of the estimation while reducing the number of samples. However, non-response rate of take-all stratum has increased significantly and the sample substitution is not possible because the non-response in the take-all stratum affects the accuracy of the estimation. It is important to adjust the bias appropriately if non-response is affected by the variable of interest. In this study, a bias adjusted estimation is proposed as an appropriate method to deal with a non-response in the take-all stratum. In particular, the estimator proposed by Chung and Shin (2020) was applied to the bias adjustment for the take-all stratum; therefore, we suggest a new method to adjust properly for the take-all stratum. The superiority of the proposed estimator was examined through simulation studies and confirmed through actual data analysis.

• The Korean Journal of Applied Statistics
• /
• v.27 no.3
• /
• pp.501-512
• /
• 2014

Modified cut-off sampling is widely used for highly skewed data. A serious drawback of modified cut-off sampling is the difficulty of adjustment of non-response in take-all stratum. Therefore, solutions of the problems of non-response in take-all stratum have been studied in various ways such as substitute of samples, imputation or re-weight method. In this paper, a new cut-off point based on minimizing MSE being used in exponential and power functions is suggested and it can be reduced the number of take-all stratum. We also investigate another cut-off point determination method with underlying distributions such as truncated log-normal and truncated gamma distributions. Finally we suggest the optimal cut-off point which has a minimum of take-all stratum size among suggested methods. Simulation studies are performed and Labor Survey data and simulated data are used for the case study.

• The Korean Journal of Applied Statistics
• /
• v.22 no.6
• /
• pp.1277-1287
• /
• 2009

For stratifying skewed populations, the Lavall$\acute{e}$e-Hidiroglou(LH) algorithm is often considered to have a take-all stratum with the largest units and some take-some strata with the middle-size and small units. Related to its iterative nature have been reported some numerical difficulties such as the dependency of the ultimate stratum boundaries to a choice of initial boundaries and the slow convergence to locally-optimum boundaries. The geometric stratification has been recently proposed to provide initial boundaries that can avoid such numerical difficulties in implementing the LH algorithm. Since the geometric stratification does not pursuit the optimization but the equalization of the stratum CVs, the corresponding stratum boundaries may not be (near) optimal. This paper revisits these issues concerning convergence and near-optimality of optimal stratification algorithms using artificial numerical examples. We also discuss the formation of the strata and the sample allocation under the optimization process and some aspects related to discontinuity arisen from the finiteness of both population and sample as well.

• Proceedings of the Korean Association for Survey Research Conference
• /
• 2003.06a
• /
• pp.29-33
• /
• 2003

In business survey. cut off sampling is usual. The contribution from cut off part of the population is at least small in comparison with the remaining population. In this study. the population have been separated as three stratum, cut-off. take-some, take-all, and we will estimate cut-off part.

• The Korean Journal of Applied Statistics
• /
• v.9 no.2
• /
• pp.161-169
• /
• 1996

In the design of the sampling, it is important to make a decision about the size of the sample to be selected from the population. We often have a problem to get the optical size of the sample to be considered for cost and time expended for selecting sample unit from highly skewed population. In this case, we give a graphical criterion with Take-all Stratum rate to choose a method and also illustrate the efficiency between the Neyman allocation and the cut-off method with real data.

• Archives of Plastic Surgery
• /
• v.34 no.5
• /
• pp.587-592
• /
• 2007

Purpose: In case of postburn flexion contracture of the fingers, skin graft, geometrical relaxation techniques, local flap, and free flap have been used. Among these procedures, full-thickness skin grafts from the inguinal area are widely used to reconstruct a postburn flexion contracture in the fingers. But there are many esthetic and functional problems in this procedure. Especially, hyperpigmentation of the skin-grafted fingers poses a troublesome problem, particularly in the patients who have dark colored skin. To solve the problem, we have used pulp graft which was harvested from the lateral aspect of great toe. In the present study, we report pulp graft, with which we have obtained a good result in the treatment of postburn flexion contracture of the fingers. Methods: Between September of 2004 and August of 2006, great toe pulp graft was performed to 20 sites of 15 patients. After release of the postburn flexion contracture using Z-plasty, the composite tissue (pulp) harvested from the lateral aspect of great toe was grafted on the raw surface. Moisture dressing with ointment and foam dressing material was performed. Stratum corneum of the graft got stripped off in two to four weeks after pulp graft. The color of the pulp graft was slightly reddish, then it became similar to the adjacent tissue. Results: There was complete take in all the patients who were treated with pulp graft. Great toe pulp graft provided similar color and texture to the adjacent skin, high rate of graft take, and left only a minimal scar at donor site. Conclusion: Thick keratin layer and inelastic nature of the pulp make this type of the graft much easier and simpler, and ensure a better take. Pulp graft is useful method for the reconstruction of the postburn flexion contracture in fingers.