• Title/Summary/Keyword: two sample t-test

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Goodness-of-Fit-Test from Censored Samples

  • Cho, Young-Suk
    • Journal of the Korean Data and Information Science Society
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    • v.17 no.1
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    • pp.41-52
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    • 2006
  • Because most common assumption is normality in statistical analysis, testing normality is very important. The Q-Q plot is a powerful tool to test normality with full samples in statistical package. But the plot can't test normality in type-II censored samples. This paper proposed the modified the Q-Q plot and the modified normalized sample Lorenz curve(NSLC) for normality test in the type-II censored samples. Using the two Hodgkin's disease data sets and the type-II censored samples, we picture the modified Q-Q plot and the modified normalized sample Lorenz curve.

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A note on the sample size determination of sequential and multistage procedures

  • Choi, Kiheon
    • Journal of the Korean Data and Information Science Society
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    • v.23 no.6
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    • pp.1279-1287
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    • 2012
  • We particularly emphasized how to determine the number of replications with sequential and multistage procedures. So, the t-test is used to achieve some predetermined level of accuracy efficiently with loss function in the case of normal, chi-squared, an exponential distributions. We provided that the relevance of procedures are sequential procedure, two-stage procedure, modified two-stage procedure, three-stage procedure and accelerated sequential procedure. Monte Carlo simulation is carried out to obtain the stopping sample size that minimizes the risk.

Detecting differentially expressed genes from a mixed data set

  • Lee, Sun-Ho;Kim, In-Young;Kim, Sang-Cheol;Rha, Sun-Young;Chung, Hyun-Chel;Kim, Byung-Soo
    • Proceedings of the Korean Statistical Society Conference
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    • 2003.10a
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    • pp.173-177
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    • 2003
  • When we have both a paired data set and two independent data sets, neither a paired t-test nor a two-sample t-test can be used to detect differences between two samples. In order to identify differentially expressed genes in a mixed data set, a new test statistic is proposed.

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A Two Sample Test for Functional Data

  • Lee, Jong Soo;Cox, Dennis D.;Follen, Michele
    • Communications for Statistical Applications and Methods
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    • v.22 no.2
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    • pp.121-135
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    • 2015
  • We consider testing equality of mean functions from two samples of functional data. A novel test based on the adaptive Neyman methodology applied to the Hotelling's T-squared statistic is proposed. Under the enlarged null hypothesis that the distributions of the two populations are the same, randomization methods are proposed to find a null distribution which gives accurate significance levels. An extensive simulation study is presented which shows that the proposed test works very well in comparison with several other methods under a variety of alternatives and is one of the best methods for all alternatives, whereas the other methods all show weak power at some alternatives. An application to a real-world data set demonstrates the applicability of the method.

Two Sample Test Procedures for Linear Rank Statistics for Garch Processes

  • Chandra S. Ajay;Vanualailai Jito;Raj Sushil D.
    • Communications for Statistical Applications and Methods
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    • v.12 no.3
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    • pp.557-587
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    • 2005
  • This paper elucidates the limiting Gaussian distribution of a class of rank order statistics {$T_N$} for two sample problem pertaining to empirical processes of the squared residuals from two independent samples of GARCH processes. A distinctive feature is that, unlike the residuals of ARMA processes, the asymptotics of {$T_N$} depend on those of GARCH volatility estimators. Based on the asymptotics of {$T_N$}, we empirically assess the relative asymptotic efficiency and effect of the GARCH specification for some GARCH residual distributions. In contrast with the independent, identically distributed or ARMA settings, these studies illuminate some interesting features of GARCH residuals.

Compared to Bone Mineral Density between Dominant Side and Recessive Side in Normal Elderly and Stroke Patients (정상노인과 뇌졸중 환자의 우세측과 비우세측의 골밀도 비교)

  • Min, Dong-Ki
    • PNF and Movement
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    • v.11 no.2
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    • pp.127-134
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    • 2013
  • Purpose : The purpose of this study of normal elderly and stroke patients by comparing the dominant side and recessive side was to evaluate the differents between each Methods : Thirty-two elderly participated in this study. They were classified two groups: stroke patients group and the normal elderly group. Outcome measures were: general characteristics and BMD. General characteristics included age, height, weight and body mass index. BMD was represented in the osteoporosis index, T-score and Z-score. The measurements of bone mineral density were evaluated on the calcaneus region of the dominant and recessive side, using OsteoPro. The data analyzed using SPSS 17.0 software and the Paired-sample T-test and the Independent-sample T-test Results : OI, T-score, Z-score showed no significant differences between dominant side and recessive side in normal elderly group. But stroke patients group showed OI, T-score, Z-score significant differences between paretic side and nonparetic side. Change score subtracted recessive side from dominant side was significant differences between stroke patients group and normal elderly group. Conclusion : There is positive relationship between physical activity and BMD in stroke patients. Therefore, improved physical activity can have a beneficial effect by reducing osteoporosis in stroke patients, considering a positive relationship between physical activity and BMD.

The change of muscle dysmorphia through bodybuilding for 12 weeks : Korean college students

  • Kim, Deokjin
    • International Journal of Advanced Culture Technology
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    • v.7 no.2
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    • pp.1-6
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    • 2019
  • The central purpose of the current research is to identify how 12-week bodybuilding exercise affects muscle dysmorphia. The research subjects consisted of an experimental group and a control group, each with 16 freshmen at college. MDI(muscle dysmorphic inventory), developed by Schlundt, Woodford, Brownlee(2000) was utilized to collect relevant data, which was analyzed by PASW 18.0. An independent two sample t-test was conducted to see whether there exists any significant difference between the two groups in the pre- and the post-tests. A paired t-test, in turn, was performed to identify whether there is any difference between the two tests for each group. The statistical significance level was set at p<.05. It was found that the experimental group marked a higher level of muscle dysmorphia than the control group in the pre-test. It was also found that muscle dysmorphia of the experimental group increased in the post-test, while no significant difference was manifested in the control group in the post-test.

The Effect on The Result, in Case of the In-vitro Test Performance after an Imaging Test (핵의학 영상검사 후 시행된 핵의학 검체검사에서의 영향)

  • Moon, Ki Choon;Kwon, Won Hyun;Kim, Jung In;Lee, In Won
    • The Korean Journal of Nuclear Medicine Technology
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    • v.18 no.1
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    • pp.149-152
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    • 2014
  • Purpose: At our hospital blood is collected from a patient before an imaging test, with the concern of any effect possible when a nuclear medicine imaging test and an in-vitro test are carried out at the same time. However, occasionally, the blood collection is performed after an imaging test, with the reasons that the patient is not properly guided or the patient doesn't follow the guide correctly. In that case, we prefer to gather blood again after a few days. The purpose of this study is not only to see whether there is any effect of an imaging test on the result of the in-vitro test performed with the blood collected after the imaging test, but also to study how many days waiting after each test is appropriate to take a blood sample, if the effect exists. Materials and Methods: From September to October 2013, blood were collected from 13 patients in our hospital regardless of age and sex each time before and after the injection of the radioactive isotope from the tests : PET-CT, Gated Myocardial SPECT, and DTPA GFR Scan. Considering a half-life, AFP, CA19-9, CEA, TSH, and T3 were carried out right after the blood collection. In case of an iodine therapy, blood were taken each time before and after taking radioactive iodine, and, after AFP, CA19-9, and CEA, the difference between them in consistency and in cpm were compared. Results: With 10 patients after the imaging tests and 3 patients after the iodine therapy, their serum cpm was over 10,000. Over time, the cpm decreased in accordance with the half-life ($^{18}F$ 110minutes, $^{99}mTc$ 6hours, $^{201}Tl$ 72hours, $^{131}I$ 7days). Between the two cases, one before and the other after the injection of the radioactive isotope, the cpm and the results of AFP, CA19-9, CEA, TSH, and T3 from three patients each test, PET-CT, Gated Myocardial SPECT, and DTPA GFR Scan, were very similar. In addition, in case of an iodine therapy, there was also not a meaningful difference in the cpm and the results of AFP, CA19-9, and CEA, from three patients in an iodine therapy, between the two cases, one before and the other after taking the radioactive iodine. Conclusion: In case a blood collection was performed after the imaging test which required a radioactive isotope injection, the cpm increased, differently according to the kind of the radioactive isotope. However, the results of the in-vitro tests like AFP, CA19-9, CEA, TSH, T3, etc were nearly not affected. As the result, it's considered that there will not be any significant effect also from other tests, as the result from the performed seven tests.

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A Nonparametric Test for Clinical Trial with Low Infection Rate

  • Mark C. K. Yang;Donguk Kim
    • Communications for Statistical Applications and Methods
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    • v.5 no.3
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    • pp.707-722
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    • 1998
  • This paper evaluates a new clinical trial designs for low infection rate disease. This type of sparse disease reaction makes the traditional two sample t-test or Wilcoxon rank-sum test inefficient compared to a new test suggested. The new test, which is based solely on the larger changes, is shown to be more effective than existing method by simulation for small samples. However, this test can be shown to be connected to the locally most powerful rank test under certain practical conditions. This design is motivated in testing the treatment effects in periodontal disease research.

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Effect of Vitamin C Supplementation on Blood Sugar and Serum Lipid in NIDDM Patients (비타민 C 보충이 인슐린 비의존형 당뇨병 환자의 혈당 및 혈청지질에 미치는 영향)

  • Lee, Yun-Mi;Park, Hyoung-Sook
    • The Korean Journal of Rehabilitation Nursing
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    • v.5 no.2
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    • pp.99-112
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    • 2002
  • The purpose of this study is to determine the effect of oral vitamin C supplements on blood sugar and serum lipid level(total cholesterol, triglyceride, high density lipoprotein, low density lipoprotein) in non-insulin independent diabetes mellitus. The study design was a non equivalent control group pre-test post-test design. Data for the study were collected from June 24 to August 31, 2001. The ninty-five research subject were assigned to experimental group(51) and control group(44). Vitamin C(3g/day) was given to 51 subjects for 4 weeks. Following a 12h overnight fasting, blood sample was obstaind at baseline and at the end of 4week - supplementation. Blood samples were taken for plasma vitamin C concentration, fasting blood sugar, HbA1c and serum lipid level. The pre-equivalent test was used by Chi-squre, t-test and two group's pre and post experimental differences were analyzed by t-tset to compare with each other. The results of this study were as follows ; 1. The difference between the two groups in plasma vitamin C concentration was significant(t=-12.950, p=.000). 2. The difference between the two groups in fasting blood sugar was significant(t=5.293, p=.000). 3. The difference between the two groups in HbA1c was not significant(t=1.758, p=.082). 4. The difference between the two groups in total cholesterol, HDL, LDL was significant(t=3.786, p=.000 ; t=-5.515, p=.000 ; t= 4.169, p = .000). These results suggest that megadose vitamin C supplementation be effective in lowering fasting blood sugar, serum lipids and increasing plasma vitamin C. Thus dietary measures to increase plasma vitamin C may be on important health strategy for reducing the compliance of diabetic patients.

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