问题如下：
Based on Exhibit 2, Vasileva should compute the:
选项：
A.coefficient of determination to be 0.4689.
95% confidence interval for the intercept to be –0.0037 to 0.0227.
95% confidence interval for the slope coefficient to be 0.0810 to 0.3898.
解释：
C is correct. The confidence interval for the slope coefficient is calculated as:
Confidence interval = b1 ± t c * sb1
Where b1 = 0.2354, sb1 = 0.0760 and tc = 2.032
The lower limit for the confidence interval = 0.2354 – (2.032 × 0.0760) = 0.0810
The upper limit for the confidence interval = 0.2354 + (2.032 × 0.0760) = 0.3898
note里面的关键值是1.691，哪些情况下是用这个关键值？为什么这道题用的是答案中的关键值2.032？而且我没有在文章中看到这个值，考试的时候，这个值是要背出来的吗？
