NO.PZ2015120604000123
问题如下：
Which of the following is most likely to be true for t-distribution?
选项：
A.As the sample size gets larger, the t-distribution approaches the normal distribution.
B.The degrees of freedom is equal to n.
C.The distribution is symmetry but more peaked than a standard normal distribution.
解释：
A is correct.
B is incorrect because the degrees of freedom is equal to n-1.
C is incorrect because t-distribution is less at the peak than a standard normal distribution.
在t分布中，自由度为：n-1；并且t分布的图相比正态分布要扁一些，所以B&C选项描述错误；而选项A为正确描述。
自由度的作用是什么？
