不是很懂为什么不选B

NO.PZ202306130100003505问题如下 Using information from Exhibit 2, the 99 percent prection intervfor Amtex share return for Month 37 is best scribeas: A.Yˆ f ± 0.0053.B.Yˆ f ± 0.0469.C.Yˆ f ± 0.1279. C is correct. The precteshare return is 0.0095 + [0.2354 × (−0.01)] = 0.0071.The lower limit for the prection intervis 0.0071 − (2.728 × 0.0469) = −0.1208, anthe upper limit for the prection intervis 0.0071 + (2.728 × 0.0469) =0.1350.A is incorrebecause the boun of the intervshoulbaseon the stanrerror of the forecast anthe critict-value, not on the meof the pennt variable.B is incorrebecause boun of the intervare baseon the proof the stanrerror of the forecast anthe critict-value, not simply the stanrerror of the forecast. 请问，什么时候用单尾？

NO.PZ202306130100003505 问题如下 Elena Vasileva recently joineEnergyInvest a junior portfolio analyst. Vasileva’s supervisor asks her to evaluate a potentiinvestment opportunity in Amtex, a multinationoil angcorporation basein the UniteStates. Vasileva’s supervisor suggests using regression analysis to examine the relation between Amtex shares anreturns on cru oil.Vasileva notes the following assumptions of regression analysis:■ Assumption 1. The error term is uncorrelateacross observations.■ Assumption 2. The varianof the error term is the same for all observations.■ Assumption 3. The pennt variable is normally stributeVasileva runs a regression of Amtex share returns on cru oil returns using the monthly ta she collecte Selecteta usein the regression are presentein Exhibit 1, anselecteregression output is presentein Exhibit 2. She uses a 1 percent level of significanin all her tests.Critict-values for a 1 percent level of significance:One-si left si: −2.441One-si right si: +2.441Two-si ±2.728Vasileva expects the cru oil return next month, Month 37, to −0.01. She computes the stanrerror of the forecast to 0.0469. Using information from Exhibit 2, the 99 percent prection intervfor Amtex share return for Month 37 is best scribeas: A.Yˆ f ± 0.0053. B.Yˆ f ± 0.0469. C.Yˆ f ± 0.1279. C is correct. The precteshare return is 0.0095 + [0.2354 × (−0.01)] = 0.0071.The lower limit for the prection intervis 0.0071 − (2.728 × 0.0469) = −0.1208, anthe upper limit for the prection intervis 0.0071 + (2.728 × 0.0469) =0.1350.A is incorrebecause the boun of the intervshoulbaseon the stanrerror of the forecast anthe critict-value, not on the meof the pennt variable.B is incorrebecause boun of the intervare baseon the proof the stanrerror of the forecast anthe critict-value, not simply the stanrerror of the forecast. 本题的完整解题思路