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• - [Instructor] We're told a sociologist studying fertility

• in Argentina and Bolivia wanted to test

• if there was a difference in the average number

• of babies women in each country have.

• The sociologist obtained a random sample

• of women from each country.

• Here are the results of their test.

• So they take a sample of 75 women in Argentina,

• and these women had a mean of 2.4 babies each,

• with a standard deviation of 1.5.

• And then the standard error of the mean was 0.17.

• And then they calculated similar statistics for Bolivia.

• And then they give us the t test

• for the means being different,

• and we were able to calculate these statistics.

• And they say assume that all conditions

• for inference have been met.

• At the alpha equals 0.05 level of significance,

• is there sufficient evidence to conclude

• that there is a difference in the average number

• of babies women in each country have?

• So pause this video, and see if you can answer that.

• All right, now let's work through this together.

• So this is classic hypothesis testing right over here,

• where your null hypothesis is actually going to be

• that your means are the same,

• so that the mean in Argentina is equal

• to the mean in Bolivia.

• And then your alternative hypothesis is

• that your means are different.

• And what you do is you say, all right,

• if we assume the null hypothesis, what is the probability

• that we would have gotten means this far apart?

• And that's what our p-value tells us,

• that we have a 0.31 probability,

• or a 31% probability, of getting means this far apart.

• Now, if your probability, assuming the null hypothesis,

• is below your level of significance,

• your alpha right over here,

• then you would say, all right,

• that seems like such a low probability.

• I'll reject the null hypothesis,

• which suggests the alternative hypothesis.

• But in this situation here,

• if we compare our p to our alpha,

• we see that our p-value is for sure greater than our alpha.

• So in this situation,

• I mean you could see it right over here,

• 0.31 is for sure greater than 0.05.

• So in this situation, we cannot reject the null hypothesis,

• cannot reject

• our null hypothesis.

• And so there is not sufficient evidence

• to conclude that there is a difference

• in the average number of babies women in each country have.

- [Instructor] We're told a sociologist studying fertility

B1 中級

# 用P值進行兩個樣本t檢驗的結論 (Conclusion for a two sample t test using a P value)

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林宜悉 發佈於 2021 年 01 月 14 日