发现风险Detection Risk ：
This is the risk that the auditor's procedures will not detect a misstatement that exists in an assertion that could be material either individually or when aggregated with other misstatements.
2 个原因：Auditor does not, and cannot, examine all available evidence 1)没有做，2)也做不完
抽样风险Sampling risk ：
抽样调查 VS 总体调查，抽样以偏概全，会有结论偏差。
Sampling risk is the risk that auditor’s conclusion, based on a sample, may be different from the conclusion that would have been reached if the entire population were subjected to the same audit procedure. Sampling
risk must be reduced to an acceptably low level.