老师你好，这里怎么看出它是一元线性回归

问题如下：

Determine if this proposition is correct: In a simple linear regression, the appropriate number of degrees of freedom for the critical t-value used to calculate a confidence interval equals to the number of observations minus two.

选项：

A.

correct.

B.

incorrect, because the number of degrees of freedom for the critical t-value used to calculate a confidence interval is the number of observations.

C.

incorrect, because the number of degrees of freedom for the critical t-value used to calculate a confidence interval is the number of observations minus one.

D.

incorrect, because the number of degrees of freedom for the critical t-value used to calculate a confidence interval is uncertain.

解释：

A is correct.

考点：Hypothesis Test and Linear Regression

解析：在一元线性回归中，用于用t检验值构造置信区间的自由度数量，等于样本数减去2。因此命题正确。