问题如下图：
选项：
A. 
B. 
C. 
D. 
解释：
请贴一下z检验公式
NO.PZ2016070202000006问题如下 Tycoon Bank announceththere were eight ys in the previous yefor whilosses exceethe ily 99% VAR. a result, concerns emergeabout the accuraof the Vimplementation. Assuming ththere are 250 ys in the year, whiof the following statements is/are correct?I. Using a two-taile99% confinlevel z-score test, the current Vimplementation unrstates the acturisk in the bank's portfolio.II. Using a two-taile99% confinlevel z-score test, the current Vimplementation overstates the acturisk in the bank's portfolio.III. The bank's exception rates for Vminaccurate if the bank's portfolio changes incorporate the returns from low-risk but highly profitable intray market making activities.IV. If these eight exceptions all happenein the previous month, the mol shoulreexaminefor faulty assumptions aninvaliparameters. A.I anIIIB.I, III, anIVC.Ill onlyI, II, anIVThe z-score gives 8−2.5250×0.01×0.99=3.5\frac{8-2.5}{\sqrt{250\times0.01\times0.99}}=3.5250×0.01×0.998−2.5=3.5 This is too high (greater th2.58), whilea to rejection of the null ththe Vmol is well calibrate Hence, Vis too low anstatement I. is correct. Statement II. is incorrect. However, this me to intray trang, so III. is correct, too. Finally, if all eight exceptions occurrein the last month, there is bunching, anthe mol shoulreexamine so IV. is correct.老师，III的意思是说，因为日内交易使头寸中少了很多风险小、收益高的资产，所以剩下头寸的亏损情况就变了，最终会出现很多exception么？
NO.PZ2016070202000006 截图中的公式是怎么算的，原理是怎样？
NO.PZ2016070202000006 能一下Ⅲ吗？有点没太明白
NO.PZ2016070202000006 当V天数越大，那算出来p-value 大 月会就拒绝，怎么是 overestimate ,明明是unrestimate ma
NO.PZ2016070202000006 I, III, anIV Ill only I, II, anIV The z-score gives 8−2.5250×0.01×0.99=3.5\frac{8-2.5}{\sqrt{250\times0.01\times0.99}}=3.5250×0.01×0.99 8−2.5=3.5 This is too high (greater th2.58), whilea to rejection of the null ththe Vmol is well calibrate Hence, Vis too low anstatement I. is correct. Statement II. is incorrect. However, this me to intray trang, so III. is correct, too. Finally, if all eight exceptions occurrein the last month, there is bunching, anthe mol shoulreexamine so IV. is correct.请问这里的VAR是如何判断出是被低估了呢？
