问一道题：NO.PZ201512020300000404

问题如下：

4. In response to Question 4, the 95 percent confidence interval for the regression coefficient for the default spread is closest to:

选项：

0.13 to 5.95.

1.72 to 4.36.

1.93 to 4.15.

解释：

B is correct.

The confidence interval is computed as $a_1\pm s(a_1)\times t(95\%,\infty)$. From Exhibit 1, a₁ = 3.04 and t(a₁) = 4.52, resulting in a standard error of a₁ = s(a₁) = 3.04/4.52 = 0.673. The critical value for t from Exhibit 3 is 1.96 for p = 0.025. The confidence interval for a₁ is 3.04 ± 0.673 × 1.96 = 3.04 ± 1.31908 or from 1.72092 to 4.35908.