Many researchers in various study fields use the two sample t - test to confirm their treatment effects. The two sample t - test is generally used for small samples, and assumes that two independent random samples are selected from normal populations, and the population variances are unknown. Researchers often conduct t - test, the test of equality of variances, before testing the treatment effects, and the test statistic or confidence interval for the two sample t - test has two formats according to whether the variances are equal or not. Researchers using the two sample t - test often want to know how large sample sizes they need to get reliable test results. This research gives some guidelines for sample sizes to them through simulation works. The simulation had run for normal populations with the different ratios of two variances for different sample sizes ( ≤ 30 ). The simulation results are as follows. First, if one has no idea equality of variances but he/she can assume the difference is moderate, it is safe to use sample size at least 20 in terms of the nominal level of significance. Second, the power of t - test for the equality of variances is very low when the sample sizes are small (< 30 ) even though the ratio of two variances is equal to 2. Third, the sample sizes at least 10 for the two sample t - test are recommendable in terms of the nominal level of significance and the error limit.
목차
Abstract 1. Introduction 2. Effective Sample Sizes for Two Sample t-test 2.1 Effective Sample Sizes when the Inequality of Population Variances Ignored 2.2 Effective Sample Size for the test of Homogeneity Between Two Population Variances 2.3 Effect of Sample Size on the Reliability of Two Sample t-test 2.4 Generalization 3. Conclusion Acknowledgements References
키워드
HomogeneityPower of TestSample SizesTest ReliabilityTwo Sample t - test
저자
Sunyeong Heo [ Department of statistics, Changwon National University, Changwon ]
Corresponding Author
조선대학교 기초과학연구원 [The Natural Science Research Institute of Chosun]
설립연도
2008
분야
자연과학>자연과학일반
소개
본 연구원은 기초과학을 진흥하기 위한 연구·교육 및 그 보급을 목적으로 한다. 이 목적을 달성하기 위하여 다음 각 호의 사업을 수행한다.
1. 기초과학 제 분야에 관한 조사와 연구
2. 기초과학에 관한 학술행사(학술대회, 학술세미나, 심포지엄, 초청강연회 등) 개최
3. 학문후속세대 및 일반인을 위한 기초과학 교육
4. 기관지『조선자연과학논문지』 발간
5. 『자연과학연구총서』, 『자연과학번역총서』 등 단행본 발간
6. 기타 본 연구원의 목적과 관련된 사업
간행물
간행물명
통합자연과학논문집(구 조선자연과학논문집) [Journal of Integrative Natural Science]