1) Accordingly, if the auditor discovers 3 deviations in a sample of 150, (s)he can state at a 95% confidence level (the complement of a 5% risk of overreliance) that the true occurrence rate is not greater than 5.1%.
2) The difference between the achieved UDL determined from a standard table and the sample rate (3 /150 = 2%) is the allowance for sampling risk (achieved precision). In the example, it is 3.1% (5.1% - 2%).
3) When the sample deviation rate exceeds the expected population deviation rate the achieved UDL exceeds the tolerable rate at the given risk of overreliance. In that case, the sample does not support the planned reliance on the control. For example, if the sample rate is 4% (6 deviations), the UDL is 7.8, which exceed the 6% tolerable rate.
4) When the sample deviation rate does not exceed the expected population deviation rate, the achieved UDL does not exceed the tolerable rate at the given risk level. Thus, the sample supports the planned reliance on the control. In the example, the sample deviation rate (2%) does not exceed the expected population rate (2.5%). Therefore, the achieved UDL (5.1%) does not exceed the tolerable rate (6%).