问题如下图：
您好，答案我没有理解，麻烦解释一下，谢谢。
袁园_品职助教 · 2020年04月23日
同学你好！
我看你的提问里没有解析，我先贴一下
In the absence of any other data, the bank would assume that the mean cyber loss is 300/100 or three times its mean external fraud loss (i.e., 150), and that the standard deviation of cyber risk losses is 1,600/800, or twice its standard deviation of external fraud loss (i.e., 80).
题目已知银行自己 fraud loss 的数据和 vendor的 fraud loss 和 cyber risk 数据，要求我们估计银行 cyber risk 的数据，答案里告诉我们，可以利用 cyber risk 和 fraud loss 之间的关系来求。
例如，vendor 那边的数据显示，cyber risk mean 是 fraud loss mean 的 300/100 = 3 倍，所以我们可以认为银行的 cyber risk mean 也是 fraud loss mean 的 3 倍，所以银行的 cyber risk mean = 3*50 = 150；standard deviation 同理
NO.PZ2020011303000149 问题如下 A bank estimates from its own ta thexternfraulosses have (in USmillions) a meof 50 ana stanrviation of 40. The ta from a venr shows thexternfrauha meof 100 ana stanrviation of 800. It also shows thcyber risk ha meof 300 ana stanrviation of 1,600. The bank hno ta on cyber risk losses. How shoulit estimate the meanstanrviation for its cyber risk losses? In the absenof any other tthe bank woulassume ththe mecyber loss is 300/100 or three times its meexternfrauloss (i.e., 150), anththe stanrviation of cyber risk losses is 1,600/800, or twiits stanrviation of externfrauloss (i.e., 80). 题目问一家银行根据自己的数据估计，外部欺诈损失（以百万美元计）的平均值为 50，标准差为 40。来自供应商venr的数据显示，外部欺诈的平均值为 100，标准差为 800。它还显示网络风险的平均值为 300，标准差为 1,600。该银行没有关于cyber risk损失的数据。它应该如何估计其Cyber risk损失的均值和标准差？可以利用 cyber risk 和 frauloss 之间的关系来求。例如，venr 那边的数据显示，cyber risk me是 frauloss me的 300/100 = 3 倍，所以我们可以认为银行的 cyber risk me也是 frauloss me的 3 倍，所以银行的 cyber risk me= 3*50 = 150；stanreviation 同理。 请问这是什么估计方法？在基础课、讲义的哪部分？怎么没有印象呢？
NO.PZ2020011303000149问题如下A bank estimates from its own ta thexternfraulosses have (in USmillions) a meof 50 ana stanrviation of 40. The ta from a venr shows thexternfrauha meof 100 ana stanrviation of 800. It also shows thcyber risk ha meof 300 ana stanrviation of 1,600. The bank hno ta on cyber risk losses. How shoulit estimate the meanstanrviation for its cyber risk losses? In the absenof any other tthe bank woulassume ththe mecyber loss is 300/100 or three times its meexternfrauloss (i.e., 150), anththe stanrviation of cyber risk losses is 1,600/800, or twiits stanrviation of externfrauloss (i.e., 80). 不懂为什么这么定义？