• Communications for Statistical Applications and Methods
• /
• v.31 no.1
• /
• pp.1-35
• /
• 2024

The assumption of homoscedasticity is one of the most crucial assumptions for many parametric tests used in the biological sciences. The aim of this paper is to compare the empirical probability of type I error and the power of ten parametric and two non-parametric tests for homoscedasticity with simulations under different types of distributions, number of groups, number of samples per group, variance ratio and significance levels, as well as through empirical data from an agricultural experiment. According to the findings of the simulation study, when there is no violation of the assumption of normality and the groups have equal variances and equal number of samples, the Bhandary-Dai, Cochran's C, Hartley's Fmax, Levene (trimmed mean) and Bartlett tests are considered robust. The Levene (absolute and square deviations) tests show a high probability of type I error in a small number of samples, which increases as the number of groups rises. When data groups display a nonnormal distribution, researchers should utilize the Levene (trimmed mean), O'Brien and Brown-Forsythe tests. On the other hand, if the assumption of normality is not violated but diagnostic plots indicate unequal variances between groups, researchers are advised to use the Bartlett, Z-variance, Bhandary-Dai and Levene (trimmed mean) tests. Assessing the tests being considered, the test that stands out as the most well-rounded choice is the Levene's test (trimmed mean), which provides satisfactory type I error control and relatively high power. According to the findings of the study and for the scenarios considered, the two non-parametric tests are not recommended. In conclusion, it is suggested to initially check for normality and consider the number of samples per group before choosing the most appropriate test for homoscedasticity.

• Communications for Statistical Applications and Methods
• /
• v.15 no.3
• /
• pp.333-342
• /
• 2008

Variable selection theorem in the linear regression model is extended to the analysis of covariance model. When some of regression variables are omitted from the model, it reduces the variance of the estimators but introduces bias. Thus an appropriate balance between a biased model and one with large variances is recommended.

• Journal of Korean Academy of Nursing
• /
• v.18 no.3
• /
• pp.231-238
• /
• 1988

The purpose of this study was to assess and compare discrepancy in the scores of uncertainty perceived by patients and nurses' interperson perception. For this study, 124 hospitalized patients and the same numbered nurses assigned for direct care of each 124 patients were selected from general ward of C. University Hospital in Seoul during the time period from September to November 1987. Degree of uncertainty was measured by 27 items modified from Mishel Uncertainty in Illness Scale (MUIS), and was utilized by a Likert type scale The data were analysed by Mcnemar-test. Unpaired t-test. ANOVA, Scheffe - test and Stepwise multiple regression. The results are summarized as follows : 1. The discrepancy in the scores of uncertainty perceived by patients and nurses' interperson perception showed significant differences in 23 of 27 items : 11 of 23 items showed that the scores of patients' perception of uncertainty were higher than that of nurses' interperson perception of uncertainty. but 12 of 23 items were revealed reversely. 2. With regard to nurse's demographic variables, the discrepancy scores were the higest in the group under 22 years of age (F＝3.20, p＝.026) and in the group less than 1 year of nursing experience among 4 groups (F＝4.41, p＝.006). 3. The discrepancy scores had a tendency to be lowered in the higher age group(r＝ -.27. p＝.0026) and in the longer experienced group (r＝-.25, p＝.0052). 4. The most important variable affecting the discrepancy scores was identified to be the nurses' age which acounted for 7.2% fo the total variances in the stepwise multiple regression analysis. This was followed by patient hospital days which accounted for an additional 4.5% of the total variances. To conclude, the discrepancy in the scores of uncertainty perceived by patients and nurses' interperson perception showed significant differences in 23 of 27 items. The discrepancy scores of uncertainty had a tendancy to be lowered in the higher age group and in the longer experienced group.

• Asian-Australasian Journal of Animal Sciences
• /
• v.15 no.5
• /
• pp.627-632
• /
• 2002

Genetic parameters for dairy performance traits were estimated, breeding values for the traits of all breeding sires and cows were predicted and the genetic trends were estimated using the breeding values in the Central Cattle Breeding Station (CCBS). A total of 3,801 records for Bangladeshi Local, 756 records for Red Sindhi and 959 records for Sahiwal covering the period from 1961 to 1997 were used in this analysis. Traits considered were total milk production per lactation (TLP), lactation length (LL) and daily milk yield (DMY). The genetic parameters were estimated by the REML using MTDFREML program. The breeding values were predicted by a best linear unbiased prediction (BLUP). In all sets of data, the genetic trends for the dairy performance traits were computed as averages of breeding values for cows born in the particular year. The estimates of heritability for TLP (0.26 and 0.27) and DMY (0.28 and 0.27) were moderate in Bangladeshi local and Red Sindhi breed, respectively. Furthermore, the heritability estimate for LL (0.24) was moderate in Red Sindhi. The estimates of heritabilities for all traits were low in Sahiwal. The repeatability estimate was high for TLP, moderate for LL and moderate to high for DMY. All variances estimated in Bangladeshi Local were low, comparing the respective values estimated in both Red Sindhi and Sahiwal. On the other hand, additive genetic variances for the three traits were estimated very low in Sahiwal. The genetic trends for the three dairy production traits have not been positive except for the recent trend in Bangladeshi Local.

• The Research Journal of the Costume Culture
• /
• v.11 no.1
• /
• pp.88-102
• /
• 2003

In our culture, the term, "be like", is frequently used. There are expressions such as "feminine-looking dress" and "manly style" relating to this term when we describe the styles of clothing. This study addresses the question on which type of garment would be selected under the description of the term, "be-like", in relation to gender. This term reveals the preconception of gender as being feminine or masculine according to the styles and colors of clothes. A group of 362 college students from Seoul and Gyeonggi area was surveyed fur the study The statistical analysis of SPSS 10.0 was applied f3r analyzing the data, and the significant variances were reviewed by the basic statistics, multi-variate and T-test. The results are as follows: First, the details of clothes imply the preconceived idea of gender. As a result, women's blouses and skirts were selected as the most feminine upper and bottom garments. The Y-shirt and T-shirt were selected as the most masculine upper garments. However, in contrast to the . skirts being the most feminine bottom wear, the pants were not significantly recognized as the most masculine ,clothes. Second, the variances of the survey show that the female students are more conscious of the sexual identity expressed in clothes than the male students. Third, the styles of clothes reflect the general understanding of what is considered to be "feminine or not feminine" and "masculine or not masculine" In conclusion, this study has discovered that the certain characteristics of gender are predominantly implicated in the styles length, and color of clothes. Both men and women responded differently in defining their idea of "femininity" and "masculinity". Nevertheless, there still exists strong preconception of what is considered to be feminine or masculine, and it affects the choices people make in selecting clothes.

• Communications for Statistical Applications and Methods
• /
• v.18 no.3
• /
• pp.277-286
• /
• 2011

Global companies can sell their products with dierent warranty periods based on location and times. Customers can select the length of warranty on their own if they pay an additional fee. In this paper, we consider the warranty period and the repair time limit as random variables. A two-dimensional warranty policy is considered with repair times and failure times. The repair times are considered within the repair time limit and the failure times are considered within the warranty period. Under the non-renewable warranty policy, we obtain the expected number of warranty services and their variances in the censored area by warranty period and repair time limit to conduct a warranty cost analysis. Numerical examples are discussed to demonstrate the applicability of the methodologies and results using field data based on the proposed approach in the paper.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.45 no.1
• /
• pp.38-43
• /
• 2000

The environment in which a given genotype is grown may influence its grain quality characteristics. When varieties are $\times$ evaluated over numerous environments, a variety environment interaction usually is observed, but the relative magnitude of environmental(E), genetic(G), and G $\times$ E effects on quality is unclear. In order to determine relative contribution of genotype, environment, and G $\times$ E interaction to the variations observed in grain quality characteristics, 18 Korean wheat cultivars and experimental lines were evaluated in two environments in 1998 and 1999. Correlation coefficients between grain quality and agronomic characteristics were also estimated. The analysis of variance for the optical density obtained by reaction bet- ween gliadin and anti-gliadin polyclonal antibody (AGPab) indicated that gliadin content measured by Enzyme-Linked Immunosorbent Assay(ELISA) was significantly in- fluenced by environment and cultivar differences. The significant differences of year and year $\times$ location were also found. The ratio of the variances associated with environmental effects to the variances associated with genetic effect gave relatively greater influence of environmental factor on gliadin content. The different protein content from same genotype grown in different environment might be associated with degree of storage protein accumulations. Significant relationships between ELISA and protein content, yield, ten spike weight, and ten spike number were detected. Polyphenol oxidase (PPO) activity was significantly influenced by year, location, cultivar and year $\times$ location. The variance in grain PPO activities among growing years appeared larger than the variation produced by the cultivar examined. This suggested that the growing environment contributed more to variability in grain PPO concentration.

• Journal of Korean Society for Quality Management
• /
• v.49 no.2
• /
• pp.145-159
• /
• 2021

Purpose: A statistical similarity evaluation to compare pharmacokinetics(PK) profile data between nonclinical and clinical experiments has become a significant issue on many drug development processes. This study proposes a new similarity index by considering important parameters, such as the area under the curve(AUC) and the time-series profile of various PK data. Methods: In this study, a new profile similarity index(PSI) by using the concept of a process capability index(Cp) is proposed in order to investigate the most similar animal PK profile compared to the target(i.e., Human PK profile). The proposed PSI can be calculated geometric and arithmetic means of all short term similarity indices at all time points on time-series both animal and human PK data. Designed simulation approaches are demonstrated for a verification purpose. Results: Two different simulation studies are conducted by considering three variances(i.e., small, medium, and large variances) as well as three different characteristic types(smaller the better, larger the better, nominal the best). By using the proposed PSI, the most similar animal PK profile compare to the target human PK profile can be obtained in the simulation studies. In addition, a case study represents differentiated results compare to existing simple statistical analysis methods(i.e., root mean squared error and quality loss). Conclusion: The proposed PSI can effectively estimate the level of similarity between animal, human PK profiles. By using these PSI results, we can reduce the number of animal experiments because we only focus on the significant animal representing a high PSI value.

• The Journal of the Acoustical Society of Korea
• /
• v.41 no.3
• /
• pp.326-334
• /
• 2022

In this paper, we propose speech enhancement algorithm as a pre-processing for robust speech recognition in noisy environments. Auxiliary-function-based Independent Vector Analysis (AuxIVA) is performed with weighted covariance matrix using time-varying variances with scaling factor from target masks representing time-frequency contributions of target speech. The mask estimates can be obtained using Neural Network (NN) pre-trained for speech extraction or diffuseness using Coherence-to-Diffuse power Ratio (CDR) to find the direct sounds component of a target speech. In addition, outputs for omni-directional noise are closely chained by sharing the time-varying variances similarly to independent subspace analysis or IVA. The speech extraction method based on AuxIVA is also performed in Independent Low-Rank Matrix Analysis (ILRMA) framework by extending the Non-negative Matrix Factorization (NMF) for noise outputs to Non-negative Tensor Factorization (NTF) to maintain the inter-channel dependency in noise output channels. Experimental results on the CHiME-4 datasets demonstrate the effectiveness of the presented algorithms.

• Asian-Australasian Journal of Animal Sciences
• /
• v.31 no.5
• /
• pp.636-642
• /
• 2018

Objective: The objective of this study was to estimate genetic parameters of milk, fat, and protein yields within and across lactations in Tunisian Holsteins using a random regression test-day (TD) model. Methods: A random regression multiple trait multiple lactation TD model was used to estimate genetic parameters in the Tunisian dairy cattle population. Data were TD yields of milk, fat, and protein from the first three lactations. Random regressions were modeled with third-order Legendre polynomials for the additive genetic, and permanent environment effects. Heritabilities, and genetic correlations were estimated by Bayesian techniques using the Gibbs sampler. Results: All variance components tended to be high in the beginning and the end of lactations. Additive genetic variances for milk, fat, and protein yields were the lowest and were the least variable compared to permanent variances. Heritability values tended to increase with parity. Estimates of heritabilities for 305-d yield-traits were low to moderate, 0.14 to 0.2, 0.12 to 0.17, and 0.13 to 0.18 for milk, fat, and protein yields, respectively. Within-parity, genetic correlations among traits were up to 0.74. Genetic correlations among lactations for the yield traits were relatively high and ranged from $0.78{\pm}0.01$ to $0.82{\pm}0.03$, between the first and second parities, from $0.73{\pm}0.03$ to $0.8{\pm}0.04$ between the first and third parities, and from $0.82{\pm}0.02$ to $0.84{\pm}0.04$ between the second and third parities. Conclusion: These results are comparable to previously reported estimates on the same population, indicating that the adoption of a random regression TD model as the official genetic evaluation for production traits in Tunisia, as developed by most Interbull countries, is possible in the Tunisian Holsteins.