NO.PZ202212300100014201
问题如下：
Based on Exhibit 1, Olabudo should calculate a prediction interval for the actual US CPI closest to:
选项：
A.2.7506 to 2.7544 B.2.7521 to 2.7529 C.2.7981 to 2.8019解释：
The forecast
interval for inflation is calculated in three steps:
Step 1. Make the
prediction given the US CPI forecast of 2.8:
Step 2. Compute
the variance of the prediction error:
Step 3. Compute
the prediction interval:
2.7525 ± (2.0 ×
0.0009)
Lower bound:
2.7525 − (2.0 × 0.0009) = 2.7506.
Upper bound:
2.7525 + (2.0 × 0.0009) = 2.7544.
So,
given the US CPI forecast of 2.8, the 95% prediction interval is 2.7506 to
2.7544.
请问2.7525 ± (2.0 × 0.0009)是怎么得出的？为什么？另外上面一大串的公式要背下来吗？
