文章基本信息

标题：More about the basic assumptions of t-test: normality and sample size
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作者：Tae Kyun Kim ; Jae Hong Park
期刊名称：Korean Journal of Anesthesiology
印刷版ISSN：2005-6419
出版年度：2019
卷号：72
期号：4
页码：331-335
DOI：10.4097/kja.d.18.00292
语种：English
出版社：The Korean Society of Anesthesiologists,
摘要：Most parametric tests start with the basic assumption on the distribution of populations. The conditions required to conduct the t-test include the measured values in ratio scale or interval scale, simple random extraction, normal distribution of data, appropriate sample size, and homogeneity of variance. The normality test is a kind of hypothesis test which has Type I and II errors, similar to the other hypothesis tests. It means that the sample size must influence the power of the normality test and its reliability. It is hard to find an established sample size for satisfying the power of the normality test. In the current article, the relationships between normality, power, and sample size were discussed. As the sample size decreased in the normality test, sufficient power was not guaranteed even with the same significance level. In the independent t-test, the change in power according to sample size and sample size ratio between groups was observed. When the sample size of one group was fixed and that of another group increased, power increased to some extent. However, it was not more efficient than increasing the sample sizes of both groups equally. To ensure the power in the normality test, sufficient sample size is required. The power is maximized when the sample size ratio between two groups is 1 : 1.