Sampling risk occurs because auditors test only a subset of transactions or controls rather than the complete population, creating uncertainty about whether identified issues are isolated or systemic. Statistical sampling techniques and adequate sample sizes help quantify and minimize this risk, but cannot eliminate it entirely. Auditors must balance sampling risk against audit efficiency and cost constraints. For example, testing 50 of 10,000 expense transactions might miss systematic fraud affecting the remaining population, leading auditors to issue an unqualified opinion despite material misstatements in the full dataset.