• Communications for Statistical Applications and Methods
• /
• 제11권2호
• /
• pp.297-311
• /
• 2004

In the sample survey for a highly skewed population, stratum jumpers often occur. Stratum jumpers are units having large discrepancies between a stratification variable and a study variable. We propose two models for stratum jumpers: a multiplicative model and a random replacement model. We also consider the modification of the L-H stratification algorithm such that we apply the previous models to L-H algorithm in determination of the sample sizes and the stratum boundaries. We evaluate the performances of the new stratification algorithms using real data. The result shows that L-H algorithm for the random replacement model outperforms other algorithms since the estimator has the least coefficient of variation.

• 대한수의학회지
• /
• 제48권4호
• /
• pp.457-462
• /
• 2008

The objective of this study was to determine appropriate sample size that simulated different assumptions for diagnostic test characteristics and true prevalences when designing serological surveillance plan for pullorum disease and fowl typhoid in domestic poultry production. The number of flocks and total number of chickens to be sampled was obtained to provide 95% confidence of detecting at least one infected flock, taking imperfect diagnostic tests into account. Due to lack of reliable data, within infected flock prevalence (WFP) was assumed to follow minimum 1%, most likely 5% and maximum 9% and true flock prevalence of 0.1%, 0.5% and 1% in order. Sensitivity were modeled using the Pert distribution: minimum 75%, most likely 80% and maximum 90% for plate agglutination test and 80%, 85%, and 90% for ELISA test. Similarly, the specificity was modeled 85%, 90%, 95% for plate agglutination test and 90%, 95%, 99% for ELISA test. In accordance with the current regulation, flock-level test characteristics calculated assuming that 30 samples are taken from per flock. The model showed that the current 112,000 annual number of testing plan which is based on random selection of flocks is far beyond the sample size estimated in this study. The sample size was further reduced with increased sensitivity and specificity of the test and decreased WFP. The effect of increasing samples per flock on total sample size to be sampled and optimal combination of sensitivity and specificity of the test for the purpose of the surveillance is discussed regarding cost.

• Archives of Pharmacal Research
• /
• 제3권2호
• /
• pp.65-74
• /
• 1980

Analysis of particle size distribution of a sample of fine aluminum hydroxide powder was carried out by four different methods, i. e., conductivity, air permeability, gas-adsorption and sedimentation. Each method was reproducible. The results obtained by Coulter counter and sedimentation balance were similar, and the data obtained by Lea and Nurse permeameter and Stroehlein areameter were also similar. But the results differ considerabley between the former and the latter. The advantages and disavantages of each method were discussed briefly and a means of comparing the results with those obtianed by surface area measurements was shown.

• Journal of the korean society of oceanography
• /
• 제33권3호
• /
• pp.113-122
• /
• 1998

The requisite numbers of sample replicates for the population study of soft-bottom benthos were estimated from survey data on the Songdo tidal flat and subtidal zone in Youngil Bay, Korea. Large numbers of samples were taken; two-hundred-fifty 0.02 m$^2$ box corers and fifty 0.1m$^2$ van Veen grabs were taken on the Songdo tidal flat and in Youngil Bay, respectively. The effect of sampler size on sampling efforts was investigated by pooling the unit samples in pairs, fours, eights, etc. The requisite number of sample replicates (n$_r$) was determined by sample variance (s$^2$) and mean (m) function (n$_r$:s$^2$/P$^2$m$^2$), at P=0.2 level, in which s$^2$ and m were calculated from the counts of individuals collected. For example, seven samples of 0.02 m$^2$ corer for the intertidal and two samples of 0.1 m$^2$ van Veen grab for subtidal fauna were required to estimate the total density of community. The smaller sampler size was more efficient than larger ones when sampling costs were compared on the basis of the total sampling area. The requisite number of sample replicates was also predicted ($\^{n}$n$_r$) by substituting $\^{s}$$^2$ obtained from the regression of s$^2$ against m using the Taylor's power law ($\^{s}$$^2$:am$^b$). The regression line of survey data on s$^2$ and m plotted on log scale was well fitted to the Taylor's power law (r$^2$${\geq}$0.95, p<;0.001) over the whole range of m. The exponent b was, however, varied when it was estimated from m which was categorized into classes by its scale. The fitted exponent b was large when both density class and the sampler size were large. The number of sample replicates, therefore, could be more significantly estimated, if regression coefficients (a and b) would be calculated from sample variance and mean categorized into density classes.

• 한국생태학회:학술대회논문집
• /
• 한국생태학회 1998년도 춘계공동 학술발표대회
• /
• pp.45-45
• /
• 1998

• 한국근적외분광분석학회:학술대회논문집
• /
• 한국근적외분광분석학회 2001년도 NIR-2001
• /
• pp.1129-1129
• /
• 2001

Maize, in Hungary, is the fodder-plant grown in the biggest quantity. It is not only used as a fodder but other products such as iso-sugar are made from it, too. The quality of the fodder and the produce is largely dependent on the composition of the supplied maize to the processing site. The examination of quality parameters besides conventional methods are investigated and measured by NIR spectroscopy on a routine basis. The investigated parameters are the following: water, total protein, starch and oil content. The accuracy and precision of determining these parameters we, apart from the wet chemical methods, influenced by sample preparation to a great extent. One of the main features of this is the sample particle size and its distribution across the sample. The uneven distribution of particle size negatively influences the measurement accuracy, decreases model robustness and prediction ability. With these in mind the aim of our experiment was to investigate the effect of particle size on the accuracy of maize composition determination using reflection measurement setup. In addition, we tested different spectrum transformations, which are suitable for canceling this effect. In our experiment 47 samples were analyzed with three different mesh sizes (1.5mm, 1.8mm and 2mm). The results of our findings are presented here.

• Bulletin of the Korean Chemical Society
• /
• 제28권8호
• /
• pp.1375-1382
• /
• 2007

A column preconcentration method with pulverized Amberlite XAD-4 loaded with bismuthiol I (BI) has been developed for the determination of trace Cd(II) and Cu(II) in various real samples by flame atomic absorption spectrophotometry. Various experimental conditions, such as the size of XAD-4, adsorption flow rate, amount of bismuthiol I, stirring time for adsorbing bismuthiol I on XAD-4, pH of sample solution, amount of XAD-4- BI, desorption solvent, and desorption flow rate, were optimized. Also, the adsorption capacity and the adsorption rate of Cd(II) and Cu(II) on XAD-4-BI were investigated. The interfering effects of various concomitant ions were investigated, Bi(III), Sn(II) and Fe(III) were found to affect the determination. But the interference by these ions was completely eliminated by adjusting the amount of XAD-4-BI resin to 0.70 g, although the adsorption flow rate was slower. For Cd(II) our proposed technique obtained a dynamic range of 0.5-40 ng mL-1, a correlation coefficient (R2) of 0.9913, and a detection limit of 0.3 ng mL-1. For Cu(II), the corresponding values were 2.0-120 ng mL-1, 0.9921 and 1.02 ng mL-1. To validate this proposed technique, the aqueous samples (stream water, reservoir water, tap water and wastewater), the diluted brass sample and the plastic sample, as real samples, were used. Recovery yields of 91-103% were obtained. These measured data were not different from ICP-MS data at 95% confidence level. Our proposed method was also validated using rice flour CRM (normal, fortified) samples. From the results of our experiment, we found that the technique we present here can be applied to the determination of Cd(II) and Cu(II) in various real samples.

• 응용통계연구
• /
• 제18권2호
• /
• pp.435-443
• /
• 2005

로지스틱 회귀모형에서 결정계수는 선형 회귀모형보다 다양하게 정의되며 그 값들도 매우 작아 로지스틱 회귀모형 평가기준으로 사용되는 통계량이 라고 할 수 없다. Liao와 McGee(2003)는 부적절한 설명변수의 추가 또는 표본크기의 변화에 민감하지 않은 두 종류의 수정 결정계수를 제안하였다. 본 연구에서는 실제자료에 적용한 로지스틱 회귀모형에서 수정 결정계수를 포함한 네 종류의 결정계수들을 변수선택의 기준으로 사용하여 기존의 변수선택 방법인 전진선택, 후진제거, 단계적 선택방법, AIC 통계량 등을 사용한 방법들과 비교하여 그 적절함과 효율성을 토론한다.

• 응용통계연구
• /
• 제23권5호
• /
• pp.883-890
• /
• 2010

Since Fisher's exact test is conducted conditional on the observed value of the margin, there are two kinds of the exact power, the conditional and the unconditional exact power. The conditional exact power is computed at a given value of the margin whereas the unconditional exact power is calculated by incorporating the uncertainty of the margin. Although the sample size is determined based on the unconditional exact power, the actual power which Fisher's exact test has is the conditional power after the experiment is finished. This paper investigates differences between the conditional and unconditional exact power Fisher's exact test. We conclude that such discrepancy is a disadvantage of Fisher's exact test.

• 약학회지
• /
• 제24권2호
• /
• pp.117-122
• /
• 1980

A new application of high pressure liquid chromatography for the determination of fenitrothion and cis- and trans-neopynamin in insecticidal preparations was investigated. Optimum conditions for a good separation and determination were determined; solvent system: dichloromethane + n-hexane = 17 + 83; Bow rate: 0.5ml/min; column: u-porasil ($4mm{\times}3Ocm$); absorbance wavelength: 254nm; 0.05 AUFS and sample size: 30 ul. Recovery of fenicrothion, cis- and trans-neopynamin from mixed artificial preparations was 99.6%, 99.7% and 99.8% respectively. Also reproducibility tests showed that the coefficient of variation was 0.89% for fenitrothion, 0.74% cis-neopynamin and 1.1% for trans-neopynamin. There was no interference with insecticidal preparation containing DDVP, allethrin, S-421 and kerosene. HPLC method was rapid, accurate and it gave better reproducibility and higher sensitivity than any other analytical method. It was considered that HPLC could be greatly applied to the analysis of fenitrothion and neopynamin in insecticidal preparations.