美国统计课的Take Home Exam!请求帮助!!!!!!

1. 判断题,如果是错的,请告诉我为什么.谢谢啦!!!
      

      b. The Central Limit Theorem demonstrates that, under certain conditions, small samples (n < 15) can be used to make inferences about population means.
          ***极限理论说明,在某种情况下, 在小于15的样本中, 也是用样本平均数推测总体平均数.




      c.Jane tested whether average starting salaries of recent graduates differed by degree program.
She collected salary data of random samples of recent graduates of public policy, public health, environmental studies, and political science programs.
Her analysis consisted of independent samples t-tests to compare the pairs of groups.
She conducted an appropriate analysis.
        Jane要测试是否各个专业毕业的同学毕业后起薪是否有差异. 她随机抽样了近期在公共政策,公共健康,环境研究,政治科学这些专业的毕业生. 她的分析用t test来做是否正确?


      d.Joe tested whether a relationship existed between alcohol usage and suicide rates among states, both ratio-level variables.
He used a correlation to test the relationship, which was an appropriate method of analysis.
        Joe要测试各个州之间的酒精使用率和自杀率是否有关联,都是ratio- level的变量. 他用Correlation这个测试方法来测试这个关系,是否正确?


      2. Identify three ways to reduce the standard error of a regression coefficient.(减少回归系数标准差的三种方法)




               截止时间: 中国时间周三上午10点.









b

自己顶一下~~求助求助~~~

请求帮忙啊~
其实都是很基础的统计问题~
判断题，回答起来也不会很麻烦的~
谢谢！！