没有看懂答案的解释😢
问题如下图：
选项：
A. 
B. 
C. 
解释：
菲菲_品职助教 · 2018年10月02日
同学你好，选项A的意思就是，让你比较bond和stock哪个得到负回报的概率比较大。已知bond和stock的均值和标准差，因为这两个资产的return都是服从正态分布的，所以我们首先要把这个一般的正态分布标准化，方便我们求概率。因为我们要求两者产生负回报的概率，即求P(X<0).
由图可知，红色部分的面积代表Stock产生负回报的概率，绿色面积代表Bond产生负回报的概率，绿色面积大于红色面积，所以Bond相对于Stock来说产生负回报的概率更高，A选项的描述是正确的。
对于B选项，应该是95%的概率不是99%的概率，所以错误。
对于C选项，相当于求Bond的return小于等于3%的概率，即P(X≤3%)，一样的道理，如下图所示：
所以应该是using a Z-score of 0.2，而不是0.25，C选项错误。
NO.PZ2017092702000100问题如下 analyst velops the following capitmarket projections.Assuming the returns of the asset classes are scribenormstributions, whiof the following statements is correct?A.Bon have a higher probability of a negative return thstocks.B.On average, 99% of storeturns will fall within two stanrviations of the mean.C.The probability of a bonreturn less thor equto 3% is termineusing a Z-score of 0.25.A is correct.The chanof a negative return falls in the area to the left of 0% unr a stanrnormcurve. stanrzing the returns anstanrviations of the two assets, the likelihooof either asset experiencing a negative return mtermine Z-score (stanrzevalue) = (X – μ)/σ Z-score for a bonreturn of 0% = (0 – 2)/5 = –0.40. Z-score for a storeturn of 0% = (0 – 10)/15 = –0.67. For bon, a 0% return falls 0.40 stanrviations below the mereturn of 2%. In contrast, for stocks, a 0% return falls 0.67 stanrviations below the mereturn of 10%. A stanrviation of 0.40 is less tha stanrviation of 0.67. Negative returns thus occupy more of the left tail of the bonstribution ththe stostribution. Thus, bon are more likely thstocks to experiena negative return.A可以用 标准差/平均 来比较吗C要怎么算呢
NO.PZ2017092702000100问题如下analyst velops the following capitmarket projections.Assuming the returns of the asset classes are scribenormstributions, whiof the following statements is correct?A.Bon have a higher probability of a negative return thstocks.B.On average, 99% of storeturns will fall within two stanrviations of the mean.C.The probability of a bonreturn less thor equto 3% is termineusing a Z-score of 0.25.A is correct.The chanof a negative return falls in the area to the left of 0% unr a stanrnormcurve. stanrzing the returns anstanrviations of the two assets, the likelihooof either asset experiencing a negative return mtermine Z-score (stanrzevalue) = (X – μ)/σ Z-score for a bonreturn of 0% = (0 – 2)/5 = –0.40. Z-score for a storeturn of 0% = (0 – 10)/15 = –0.67. For bon, a 0% return falls 0.40 stanrviations below the mereturn of 2%. In contrast, for stocks, a 0% return falls 0.67 stanrviations below the mereturn of 10%. A stanrviation of 0.40 is less tha stanrviation of 0.67. Negative returns thus occupy more of the left tail of the bonstribution ththe stostribution. Thus, bon are more likely thstocks to experiena negative return.老师请问A要怎么计算
NO.PZ2017092702000100问题如下analyst velops the following capitmarket projections.Assuming the returns of the asset classes are scribenormstributions, whiof the following statements is correct?A.Bon have a higher probability of a negative return thstocks.B.On average, 99% of storeturns will fall within two stanrviations of the mean.C.The probability of a bonreturn less thor equto 3% is termineusing a Z-score of 0.25.A is correct.The chanof a negative return falls in the area to the left of 0% unr a stanrnormcurve. stanrzing the returns anstanrviations of the two assets, the likelihooof either asset experiencing a negative return mtermine Z-score (stanrzevalue) = (X – μ)/σ Z-score for a bonreturn of 0% = (0 – 2)/5 = –0.40. Z-score for a storeturn of 0% = (0 – 10)/15 = –0.67. For bon, a 0% return falls 0.40 stanrviations below the mereturn of 2%. In contrast, for stocks, a 0% return falls 0.67 stanrviations below the mereturn of 10%. A stanrviation of 0.40 is less tha stanrviation of 0.67. Negative returns thus occupy more of the left tail of the bonstribution ththe stostribution. Thus, bon are more likely thstocks to experiena negative return.可以把B答案翻译一下吗？
NO.PZ2017092702000100问题如下 analyst velops the following capitmarket projections.Assuming the returns of the asset classes are scribenormstributions, whiof the following statements is correct?A.Bon have a higher probability of a negative return thstocks.B.On average, 99% of storeturns will fall within two stanrviations of the mean.C.The probability of a bonreturn less thor equto 3% is termineusing a Z-score of 0.25.A is correct.The chanof a negative return falls in the area to the left of 0% unr a stanrnormcurve. stanrzing the returns anstanrviations of the two assets, the likelihooof either asset experiencing a negative return mtermine Z-score (stanrzevalue) = (X – μ)/σ Z-score for a bonreturn of 0% = (0 – 2)/5 = –0.40. Z-score for a storeturn of 0% = (0 – 10)/15 = –0.67. For bon, a 0% return falls 0.40 stanrviations below the mereturn of 2%. In contrast, for stocks, a 0% return falls 0.67 stanrviations below the mereturn of 10%. A stanrviation of 0.40 is less tha stanrviation of 0.67. Negative returns thus occupy more of the left tail of the bonstribution ththe stostribution. Thus, bon are more likely thstocks to experiena negative return.同上，英文版的不太看得懂
NO.PZ2017092702000100 老师这题是不是因为已知了正态分布，所以不用标准化，得出来的概率就可以直接比较大小？