In place of reveiwing every transaction or document, what auditors can do is take some of them using a process called audit sampling. Sampling helps auditors to effectively get proper and timely evidence because auditing every transaction is a long and time taking process with a lot of money.
FOr auditors to make the judgement accrute on financial accurancy, internal controls, complaince and potential risks, the sample choosed must be representative of entire data. Audit sampling is said to balance cost, time and correctness while preservaing audit qulity, supporting professionalism.