1. Introduction to the Technique
Random sampling is a statistical tool used by internal auditors to select a subset of transactions or data from a larger population for testing. The goal is to provide reasonable assurance about the entire population by evaluating just a portion of it. This technique is especially helpful when auditing high-volume processes such as payroll, procurement, or expense reimbursements. At ACME Corp, Internal Auditor Auren uses random sampling to assess whether controls are consistently applied without having to review every transaction.
2. Suggested Practical Template for Random Sampling
A simple sampling worksheet should include the following columns:
Audit Objective (e.g., Validate expense reimbursements over $100)
Total Population (e.g., 3,200 transactions from Q1)
Sample Size (e.g., 30 transactions, based on audit risk)
Sample Selection Method (e.g., Random Number Generator)
Transaction Details (Date, ID, Amount, Approver)
Test Results (Pass/Fail)
Remarks (Missing receipts, late approvals, etc.)
Tools like Excel, audit software (e.g., IDEA, ACL), or even free online random number generators can be used to ensure true randomness.
3. Practical Application Example: Auditing Travel Reimbursements at ACME Corp
CEO Liora receives a concern from HR about inconsistencies in travel reimbursements. She asks Auren to conduct a focused audit. Auren meets with Project Manager Aven and the Finance Team to understand the process. The policy requires receipts for all claims above $100 and supervisor approval before payment.
Auren defines the population as all employee travel claims from January to March, totaling 1,284 entries. Using Excel’s RAND function, he selects 30 transactions at random. He requests full documentation (receipts, approvals, travel forms) for each sampled transaction.
The results reveal:
4 out of 30 transactions had missing receipts.
2 claims were approved post-payment.
One employee submitted expenses for unrelated personal items, later flagged and recovered.
Auren documents his findings and calculates an exception rate of 23%, which suggests potential issues across the full population. He reports these results to Liora with a recommendation to:
Automate pre-approval steps,
Enforce receipt attachment before processing, and
Provide refresher training on travel policies.
Random sampling helped Auren uncover control lapses efficiently and objectively, without needing to review over a thousand entries. This technique ensures fairness, supports audit conclusions, and helps management take timely corrective action. In fieldwork, sampling is a smart, scalable way to see the big picture from a small window.