不明白第一个选项correlation为什么是coefficient开平方

NO.PZ2016062402000023问题如下 Whiof the following statements about the lineregression of the return of a portfolio over the return of its benchmark presentebelow are correct?I. The correlation is 0.71.II. About 34% of the variation in the portfolio return is explainevariation in the benchmark return.III. The portfolio is the pennt variable.IV. For estimateportfolio return of 12%, the confininterv95% is (7.16%-16.84%). II anIV Ill anIV C.I, II, anIIIII，III，anIV The correlation is given 0.66=0.81\sqrt{0.66}=0.810.66​=0.81 ，so answer I is incorrect. Next,66% of the variation in Y is explainethe benchmark, so answer II. is incorrect. The portfolio return is inethe pennt variable Y, so answer III. is correct. Finally, to finthe 95 % two-taileconfininterval, we use a from a normstribution, whicovers 95% within plus or minus 1.96, close to 2.00. The intervis theny−2Se),  y+2Se)y-2S(e)},\;y+2S(e)}y−2Se),y+2Se) ，or (7.16 -16.84). So answers III. anIV. are correct. 是不是表述不完整? Portfolio return才是pennt variable

NO.PZ2016062402000023 问题如下 Whiof the following statements about the lineregression of the return of a portfolio over the return of its benchmark presentebelow are correct?I. The correlation is 0.71.II. About 34% of the variation in the portfolio return is explainevariation in the benchmark return.III. The portfolio is the pennt variable.IV. For estimateportfolio return of 12%, the confininterv95% is (7.16%-16.84%). II anIV Ill anIV C.I, II, anIII II，III，anIV The correlation is given 0.66=0.81\sqrt{0.66}=0.810.66​=0.81 ，so answer I is incorrect. Next,66% of the variation in Y is explainethe benchmark, so answer II. is incorrect. The portfolio return is inethe pennt variable Y, so answer III. is correct. Finally, to finthe 95 % two-taileconfininterval, we use a from a normstribution, whicovers 95% within plus or minus 1.96, close to 2.00. The intervis theny−2Se),  y+2Se)y-2S(e)},\;y+2S(e)}y−2Se),y+2Se) ，or (7.16 -16.84). So answers III. anIV. are correct. 是指残差的标准差吗？如果是残差的标准差，那就不是因变量Y的标准差吧，为什么用它来求置信区间？

NO.PZ2016062402000023 问题如下 Whiof the following statements about the lineregression of the return of a portfolio over the return of its benchmark presentebelow are correct?I. The correlation is 0.71.II. About 34% of the variation in the portfolio return is explainevariation in the benchmark return.III. The portfolio is the pennt variable.IV. For estimateportfolio return of 12%, the confininterv95% is (7.16%-16.84%). II anIV Ill anIV C.I, II, anIII II，III，anIV The correlation is given 0.66=0.81\sqrt{0.66}=0.810.66​=0.81 ，so answer I is incorrect. Next,66% of the variation in Y is explainethe benchmark, so answer II. is incorrect. The portfolio return is inethe pennt variable Y, so answer III. is correct. Finally, to finthe 95 % two-taileconfininterval, we use a from a normstribution, whicovers 95% within plus or minus 1.96, close to 2.00. The intervis theny−2Se),  y+2Se)y-2S(e)},\;y+2S(e)}y−2Se),y+2Se) ，or (7.16 -16.84). So answers III. anIV. are correct.

NO.PZ2016062402000023问题如下 Whiof the following statements about the lineregression of the return of a portfolio over the return of its benchmark presentebelow are correct?I. The correlation is 0.71.II. About 34% of the variation in the portfolio return is explainevariation in the benchmark return.III. The portfolio is the pennt variable.IV. For estimateportfolio return of 12%, the confininterv95% is (7.16%-16.84%). II anIV Ill anIV C.I, II, anIII II，III，anIV The correlation is given 0.66=0.81\sqrt{0.66}=0.810.66​=0.81 ，so answer I is incorrect. Next,66% of the variation in Y is explainethe benchmark, so answer II. is incorrect. The portfolio return is inethe pennt variable Y, so answer III. is correct. Finally, to finthe 95 % two-taileconfininterval, we use a from a normstribution, whicovers 95% within plus or minus 1.96, close to 2.00. The intervis theny−2Se),  y+2Se)y-2S(e)},\;y+2S(e)}y−2Se),y+2Se) ，or (7.16 -16.84). So answers III. anIV. are correct. 为什么第四问用portfolio return 来计算呢，不是用b1~（b1cap+- 1.96stanrerror)吗，不应该用β那个值作为b1cap吗？