独立样本t检验的适用条件

懿说学区（8） | SPSS统计分析（17）独立样本T检验

Yishuo school district (8) | SPSS statistical analysis (17) independent sample t-test

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上一期我们进行了单样本T检验的实例操作，了解了如何进行单样本T检验的流程。本期，我们将要继续了解关于独立样本T检验的内容。

In the last issue, we carried out the example operation of single sample t-test, and learned how to carry out the process of single sample t-test. In this issue, we will continue to learn about the t-test of independent samples.

单样本T检验时用来检验样本均值和总体均值是否具有显著性差异，而独立样本T检验是利用来自于两个总体的独立样本，来推断两个总体的均值是否存在显著性差异。

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因此，在进行假设检验时，其原假设为μ1=μ2，即假设两个总体均值相等，备择假设为μ1≠μ2，即两个总体均值不相等。

The single sample t-test is used to test whether there is a significant difference between the sample mean and the population mean, while the independent sample t-test uses independent samples from two populations to infer whether there is a significant difference between the two populations.

Therefore, in the hypothesis test, the original hypothesis is μ 1= μ 2, i.e. assuming that the mean values of the two populations are equal, the alternative assumption is μ 1≠ μ 2, that is, the average values of the two populations are not equal.

独立样本T检验采用T检验的方法，涉及两个总体，要求两组样本相互独立，即从一总体中抽取的一组样本对从另一总体中抽取的一组样本没有任何影响，两组样本的个案数目可以不相等。因此，独立样本T检验的前提是样本来自的总体应服从或近似服从正态分布，且两组样本相互独立。

Independent sample t-test adopts the method of t-test, involving two populations, requiring two groups of samples to be independent of each other, that is, a group of samples taken from one population has no impact on a group of samples taken from another population, and the number of cases of the two groups of samples can be unequal. Therefore, the premise of independent sample t-test is that the population from which the sample comes should obey or approximately obey the normal distribution, and the two groups of samples are independent of each other.

在原假设成立的基础上，独立样本T检验使用t统计量。独立样本T检验的结论在很大程度上取决于两个总体的方差是否相等。这就要求在应对两总体方差是否相等进行检验，称为方差齐性检验。

On the basis of the original hypothesis, the independent sample t-test uses T statistics. The conclusion of t-test of independent samples depends largely on whether the variances of the two populations are equal. This requires testing whether the variances of the two populations are equal, which is called variance homogeneity test.

SPSS中利用Levene F方差齐性检验方法检验两总体方差是否存在显著性差异。进行Levene F方差齐性检验，首先提出原假设H0：σ12＝σ22；执行过程中，若概率p值小于给定的显著性水平（一般为0.05），则拒绝原假设，认为两个总体的方差不等；否则认为两个总体的方差无显著性差异。

In SPSS, Levene f variance homogeneity test method is used to test whether there is a significant difference in the variance of the two populations. Conduct Levene f variance homogeneity test, and first put forward the original hypothesis H0: σ 12＝ σ 22； In the process of execution, if the probability p value is less than the given significance level (generally 0.05), the original hypothesis is rejected and the variance of the two populations is considered to be unequal; Otherwise, it is considered that the variance of the two populations has no significant difference.

在给定原假设的前提下，SPSS将检验值0代入t统计量的μ1-μ2部分，得到检验统计量观测值，并根据T分布的分布函数计算出概率p值。

Given the original hypothesis, SPSS substitutes the test value 0 into the value of t statistic μ 1- μ In part 2, the observed values of test statistics are obtained, and the probability p value is calculated according to the distribution function of t distribution.

下期预告：下一节我们将会进行独立样本T检验的实例操作。

Notice for next issue: in the next section, we will carry out the example operation of independent sample t-test.

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参考资料：百度百科，《SPSS 23 统计分析实用教程》

翻译：百度翻译

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