Auditing is sampling. The choice of right sample is crucial for the success of a good audit. Scope of audit also needs to be well defined before starting the audit. Normally evidences of non-conformances are collected through document review, observation, interviews etc. In addition there are certain advanced procedures to conduct an audit.
Physical Auditing : Usually auditors limit themselves after doing an observation of error prone area. But observation won’t help in detecting the actual defects in the system. In some cases auditors might need to verify the system physically. Consider the test process. Even though scope of auditing is different from testing/verification/validation auditors must ensure whether test/review process is executed in the right way. One method to ensure this is to do the actual testing by the auditors on a sample mode, say for example testing of the test cases which are declared as ‘passed’ by the actual testers. Organization need to define different methods for this process. And those methods should not be hurting the ego of individuals.
Quantitative procedures : Normally Auditors do the qualitative analysis of the evidences collected and come up with conclusions. But do they really look in to the metric data for analysis? In fact measurements reveal the actual performance level of an organization. So quality assurance audits must take both quantitative and qualitative aspects in to account. Data analysis can be conducted on schedule variation, effort variation, defect density, productivity etc.
Audit of QA itself : It needs to be ensured that the auditing team is performing well. Otherwise the reliability of their audit reports will be under question. For this some cross audits or external audits are recommended.
Sharing good practices. : It must be ensured that auditing is done to reveal not only the non-conformances but also the good practices. Those good practices should be shared across the organization.