What is Stop-or-Go Sampling?

Stop-or-go sampling involves the evaluation of each sample taken from a population to see if it fits a desired conclusion. The auditor stops evaluating samples as soon as there is sufficient support for the conclusion. If the initial evaluation does not support the conclusion, the person conducting the test incrementally increases the sample size and continues to test, trying to reach the desired outcome that supports the desired conclusion. The intent is to expend the least possible effort to conduct sampling.

How to Conduct Stop-or-Go Sampling

The steps involved in a stop-or-go sampling process are as follows:

Calculate the initial sample size, based on the size of the target population and your acceptable error level.
Select samples and review them.
If the number of errors found is less than your pre-set error threshold value, then stop sampling, on the grounds that the population’s error rate is probably within your acceptable error level.
If the number of errors found is greater than your pre-set error threshold value, then increase the sample size and continue reviewing more samples. If these additional samples bring the total errors below your threshold value, then stop sampling. If the additional samples continue to return a higher-than-acceptable error rate, then stop sampling and assume that the population contains an excessive number of errors.

Advantages of Stop-or-Go Sampling

Here are the primary advantages of using stop-or-go sampling:

Sampling efficiency. Stop-or-go sampling allows auditors to stop testing as soon as sufficient evidence is gathered to make a decision. This reduces the number of items that need to be tested compared to fixed-sample-size methods, especially in situations where errors are rare.
Cost-effectiveness. By reducing the number of samples tested, stop-or-go sampling can lower the time and costs associated with audit procedures, particularly in cases of low-error populations.
Adaptability. The method adapts dynamically based on the results observed during testing. If no errors or few errors are found early, the auditor can conclude testing sooner. Conversely, testing continues only if errors or concerns arise, ensuring a thorough evaluation where needed.
Enhanced focus on risk. Stop-or-go sampling is particularly useful in high-assurance, low-error-rate populations where the primary concern is detecting rare but significant issues. It directs audit efforts proportionately to where errors might exist.
Simplified decision-making. The sequential nature of the sampling process allows auditors to decide at each step whether to continue testing or stop. This incremental approach simplifies decision-making by focusing only on the information available at each stage.
Reduced over-auditing. In cases of low error rates, fixed-sample-size methods might lead to unnecessary testing of additional items that don’t contribute new insights. Stop-or-go sampling avoids this by allowing the process to terminate as soon as confidence is achieved.
Flexibility in sample design. Auditors can tailor the process to meet specific confidence levels and tolerable error thresholds, ensuring the method aligns with audit objectives and risk tolerances.

While stop-or-go sampling has these advantages, it is most effective in low-error-rate contexts and may not be suitable for all auditing scenarios, particularly those with high expected error rates or complex populations.