问题如下：
Suppose an active equity manager has earned an active return of 110 basis points, of which 80 basis points is the result of security selection ability. Explain the likely source of the remaining 30 basis points of active return.
选项：
解释：
This remainder of 30 basis points would be attributable to the return from factor tilts. A portfolio manager’s active return is the sum of two components, factor tilts and security selection. Factor tilt is the product of the portfolio manager’s higher or lower factor sensitivities relative to the benchmark’s factor sensitivities and the factor returns. Security selection reflects the manager’s ability to overweight securities that outperform or underweight securities that underperform.
老师对于这题我是这样理解的：
(1) 从portfolio return层面出发，portfolio return可以分为Factor Tilt (表示偏离benchmark的权重)和Security Selection;
(2) 从portfolio risk层面出发，portfolio risk (偏离benchmark的risk)可以分为Active Factor Risk和Active Specific Risk(security selection risk);
(3) 从Value Add层面出发，Value Add可以分为Asset Allocation和Security Selection
那么我们如何区分问题问我们的是portfolio return还是Value Add角度呢？其实如何区分portfolio return和value add？
