• Title, Summary, Keyword: Paired two sample t-test

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A Statistical Approach to Paired versus Group Comparisons (쌍체비교와 독립비교에 대한 통계적인 고찰)

  • Kim Tae-Min;Kim Sang-Boo
    • The Korean Journal of Applied Statistics
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    • v.19 no.2
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    • pp.231-240
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    • 2006
  • It is well understood that a paired comparison (paired t test) provides better precision than a group comparison (two-sample t test), when the pairing is effective (the variation within a pair is small). However, when the variation among the pairs is sufficiently small, the group comparison is likely to yield a better result. To get a statistical explanation of this, we examine the two methods through an analogy to one-way and two-way analysis of variance. We introduce a new measure, R statistic, which is the ratio of their confidence interval lengths, as a quantitative criterion for comparing the two methods. The distribution of the Rf statistic is described by t and F distribution functions. Through this characterization, we show that the paired comparison can be better than group comparison when the variation among the pairs is statistically significantly large.

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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    • 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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Relationship between Asian Dust and Asthma Disease in Seoul during 2005~2008 (황사현상이 천식질환에 미치는 영향도 분석: 2005년부터 2008년 서울지역을 중심으로)

  • Lee, Joong-Woo;Lee, Ki-Kwang
    • Journal of Environmental Science International
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    • v.20 no.4
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    • pp.493-500
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    • 2011
  • This study investigates the relationship between Asian dust and asthma disease in Seoul, using data of Asian dust occurrences and the number of treatments for asthma between 2005 and 2008. The data include the number of treatments for asthma on the basic day paired with the average number of treatments for asthma on the compared days. The compared day is defined by the day of no Asian dust in same month and day of the week as the basic day, when Asian dust occurs. Also, the basic day is expanded to the day after three days from the day of Asian dust. The paired two sample t-test for the number of treatments for asthma on the basic day and the compared days revealed that the Asian dust occurrences are correlated with the asthma disease. The number of treatments for asthma is significantly increased on the one and two days after Asian dust occurs. On the other hand, there's no significant difference in the number of treatments for asthma between the days of Asian dust occurrence and the days of no Asian dust, which implies that people usually try not to go out when Asian dust occurs.

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.

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.

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A Cross-cultural study of Body Image Perceptions between Korean and British University Students

  • Kim, Bu-Yong;Lee, Seunghee
    • Journal of Fashion Business
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    • v.19 no.6
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    • pp.14-27
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    • 2015
  • This study explores the comparison of body image, body satisfaction, and clothing behaviors between Korean and British young women. Body image was measured by two methods: visual and verbal. For the data analysis, the Statistical Package for Social Science (SPSS) Version 16.0 for Windows was used to provide descriptive statistics, an independent sample t-test, and paired sample t- tests were applied in this study. Our results show that Korean and British female college students perceived ideal-body images that were smaller than their self defined body images. The ideal and self-images were significantly different in both groups. Both groups were dissatisfied with their own body size. The study was limited to a small sample size. Future studies using more participants from a more diverse age group and ethnic groups are recommended. The study will help marketers and retailers develop new products and new markets aimed at Korean and British women related to body image and body satisfaction.

A study on the effects of a 12-week compound exercise program on obese middle school girls' leptin and insulin levels (12주 복합운동이 비만 여중생의 렙틴과 인슐린에 미치는 영향)

  • Lee, Seon-Ik;Cho, Young-Seuk;Yang, Jeong-Ok
    • Journal of the Korean Data and Information Science Society
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    • v.23 no.5
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    • pp.895-904
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    • 2012
  • This study aims to examine the effects of a 12-week compound exercise program (aerobic exercise+weight training) on obese middle school girls' leptin and insulin before and after the exercise. This is achieved by dividing obese middle school girls whose body fat percentage is over 30% into a compound exercise group (n=20) and a control group (n=20) and conducting comparative analysis on them.After the Shapiro-Wilk normality test of the variables, a two-sample t-test was performed to see if the variables have the same mean between the compound exercise and control groups. A paired t-test was also performed to see if the changes in the variables before and after the compound exercise program were statistically significant. For all the statistical analysis, the significance level was set at ${\alpha}=0.05$. The results of this study showed the leptin and insulin levels in the combined exercise group had been significantly decreased. The regular 12 weeks of combined exercise is considered to have a positive impact on leptin and insulin levels in obese schoolgirls.

The Effects of Aromatherapy on Stress and Stress Responses in Adolescents (향기요법이 고등학생의 스트레스와 스트레스 반응에 미치는 효과)

  • Seo, Ji-Yeong
    • Journal of Korean Academy of Nursing
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    • v.39 no.3
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    • pp.357-365
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    • 2009
  • Purpose: This study was done to examine the effects of aromatherapy on stress and stress responses in adolescents. Methods: A two-group cross-over design was used for this study. The experimental treatment was aroma essential oil inhalation and the placebo treatment was carrier oil inhalation using a necklace. The sample included 36 female high school students. Fisher's exact test, t-test, and paired t-test using SPSS/WIN program were used to analyze the data. Results: Stress levels were significantly lower when the students received the aroma treatment compared to when they received the placebo treatment. The stress responses except salivary IgA levels were significantly lower when the students received the aroma treatment. Conclusion: Aroma inhalation could be a very effective stress management method for high school students. Therefore, it is recommended that this program be used in clinical practice as an effective nursing intervention for high school students.

Differences in GRBAS scales and shimmer according to vocal sample types in people with vocal disorders (음성장애와 샘플유형에 따른 GRBAS 측정치 및 shimmer 비교)

  • Shin, Yu-Jeong;Hong, Ki-Hwan;Sim, Hyun-Sub
    • Phonetics and Speech Sciences
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    • v.3 no.3
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    • pp.149-155
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    • 2011
  • The purpose of the present study was to identify the differences in GRBAS scales between vocal sample types (sustained vowels and connected speech) for specific laryngeal conditions (vocal nodules, vocal polyps and vocal paralysis) and the relations between GRBAS scale and Shimmer value in each vocal sample type. In this study, the total of 60 voice samples of 30 patients (10 vocal nodules, 10 vocal polyps, 10 vocal paralysis) were examined and MDVP (Multi-dimensional Voice Program) was used to analyze Shimmer value. Three listeners rated two types of samples which were sorted randomly based on GRBAS scale. Three-way ANOVA, one-way ANOVA and paired t-test were used. The outcome of this study was as follow. 1) GRBAS scales varied in vocal sample types. Listeners tended to assess voices as better quality when they listened connected speech rather than sustained vowels. 2) G score of GRBAS and Shimmer were positively correlated with statistical significance. This results show that 1) vocal specialists should consider the sample types in evaluating the severity of voice problem and 2) G score could be a simple and clear method.

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Effects of a Fall Prevention Program on Physical Functions and Psychological Functions in Rural Elderly Women (낙상예방 프로그램이 농촌여성노인의 신체기능과 심리기능에 미치는 효과)

  • Kim, Sung-Min;Choi, Go-Ya
    • The Korean Journal of Rehabilitation Nursing
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    • v.15 no.1
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    • pp.63-71
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    • 2012
  • Purpose: The purpose of this study was to determine the effects of a fall prevention program on gait ability, one leg standing-right, one leg standing-left, fear of falling, fall efficacy, and depression in the elderly. Methods: A fall prevention program was consisted of fall preventing exercise with laughter therapy. Quasi-experimental design with one group pre- and post-test was used. Twenty-two elderly were participated in this study from a community health center located in a rural area, South Korea. SPSS/WIN 18.0 was used for descriptive analysis and paired t-test. Results: After 12 weeks with a fall prevention program, gait ability (t=3.44, p=.002), one leg standing-right (t=-3.73, p=.001), one leg standing-left (t=-4.17, p<.001) and fear of falling (t=2.12, p=.046) in the elderly were significantly improved. Conclusion: A fall prevention program was effective on physical and psychological functions. This study suggested that control groups and a larger sample should be included in order to validate the effects of a fall prevention program for the elderly. Key Words: Elderly, Fall prevention program, Physical functions, Psychological