NO.PZ202206070100000602
问题如下：
The NEXT Index data most likely reflects:
选项：
A.volatility clustering.
B.transcription errors.
C.survivorship bias.
解释：
Solution
C is correct. Survivorship bias arises when a data series only reflects companies that exist at a given moment in time and not companies that may have left prior to the given moment in time (i.e., only the surviving firms are in the data). The NEXT Index has survivorship bias as evidenced by the frequent change in its component firms because of failure and acquisition by larger non-index firms.
A is incorrect because there is no evidence of this time series phenomenon.
B is incorrect because there is no evidence of improperly recorded data.
本题考查的是survivorship bias.
C是正确的。当一个数据序列只反映了在某一特定时间存在的公司，而没有反应在该特定时间之前离开的公司时(即，只有幸存的公司存在于数据中)，生存偏差就会出现。NEXT Index存在生存偏差，表现为其组成企业因较大的非指数企业的倒闭和收购而频繁变动。
A是不正确的，因为没有证据表明该偏差的存在。
B是不正确的，因为没有错误记录数据的证据。
能否解释一下volatility clustering？
谢谢老师！
