t检验，T Test (Student’s T-Test)

Posted 2021-01-31 djx571

1、什么是T test?

t-test：比较数据的均值，告诉你这两者之间是否相同，并给出这种不同的显著性（即是否是因为偶然导致的不同）

The t test (also called Student’s T Test) compares two averages (means) and tells you if they are 
different from each other. The t test also tells you how significant the differences are;
In other words it lets you know if those differences could have happened by chance.

 例子：制药公司可能想测试一种新的抗癌药物，看看它是否能提高预期寿命。在实验中，总有一个对照组(给一组人服用安慰剂，或“糖丸”)。对照组的平均预期寿命为+5岁，而服用新药的组的平均预期寿命为+6岁。看来这种药可能有效。但这可能是一个巧合。为了验证这一点，研究人员将使用Student’s t-test来发现结果是否可以在整个人群中重复

Student’s T-tests can be used in real life to compare means. For example, a drug company may 
want to test a new cancer drug to find out if it improves life expectancy. In an experiment, 
there’s always a control group (a group who are given a placebo, or “sugar pill”). The control
 group may show an average life expectancy of +5 years, while the group taking the new drug 
might have a life expectancy of +6 years. It would seem that the drug might work. But it could 
be due to a fluke. To test this, researchers would use a Student’s t-test to find out if the 
results are repeatable for an entire population.

 2、The T Score.

T Score：是两组之间的差异与组内差异的比值。t值越大，组间差异越大。t值越小，组间的相似性越大。t得分为3表示两个组之间的差异是它们内部差异的三倍。当您运行t测试时，t值越大，结果越有可能是可重复的

The t score is a ratio between the difference between two groups and the difference within the
 groups. The larger the t score, the more difference there is between groups. The smaller the t
 score, the more similarity there is between groups. A t score of 3 means that the groups are 
three times as different from each other as they are within each other. When you run a t test, 
the bigger the t-value, the more likely it is that the results are repeatable