老师问下这道题的

NO.PZ201710100100000504 问题如下 4. Whiof Singh’s statements regarng the information ratio is correct? A.Only Statement 1 B.Only Statement 2 C.Both Statement 1 anStatement 2 C is correct. The information ratio for a portfolio of risky assets will generally shrink if cash is aeto the portfolio. Because the versifieasset portfolio is unconstraineportfolio, its information ratio woulunaffecteincrease in the aggressiveness of active weights.考点 information ratio解析 定性结论，Statement 1 正确，增加cash会导致information ratio减小。Statement 2正确，增加aggressiveness不会改变information ratio。 老师，这最后一道题如何判断有没有TC啊？我看文字上没明确说表述出来，那与表二有关么？我看表二里有TC

Only Statement 2 Both Statement 1 anStatement 2 C is correct. The information ratio for a portfolio of risky assets will generally shrink if cash is aeto the portfolio. Because the versifieasset portfolio is unconstraineportfolio, its information ratio woulunaffecteincrease in the aggressiveness of active weights. 考点 information ratio 解析 定性结论，Statement 1 正确，增加cash会导致information ratio减小。Statement 2正确，增加aggressiveness不会改变information ratio。老师 这道题可以深入一下为什么a cash会导致IR下降吗？我笔记上记了IR is unaffectethe aition of cash or the use of leverage or the aggressiveness of active weights 请问哪里错了呀 谢谢老师！

您好，根据SR^2=SRb^2+IR^2，一个risky asset的sharp ratio可以拆分成benchmark的sharp ratio和IR，在这个risky asset里增加cash，根据sharp ratio的性质左边SR肯定不会变，右边SRb是benchmark的sharp ratio，benchmark是一个固定portfolio sharp ratio应该也不会变，既然两个sharp ratio都不会变，那增加cash IR减少这个等式要怎么平衡？谢谢

    constrain funIR会收到aggressive的影响。而这题的portfolios's TC＜1，因此是constrain fun这两个comment跟在这道题下面，让我认为statement 2是错的。