Audit sampling definition
/What is Audit Sampling?
Audit sampling is the use of an audit procedure on a selection of the items within an account balance or class of transactions. The sampling method used should yield an equal probability that each unit in the sample could be selected. The intent behind doing so is to evaluate some aspect of the information. Audit sampling is needed when population sizes are large, since examining the entire population would be highly inefficient. There are multiple ways to engage in audit sampling, including the methods noted below.
Block Sampling
Under block sampling, consecutive series of items are selected for review. This technique is often used when there is a need for efficiency, especially in testing transactions that occur in batches or sequences. The block sampling process is as follows:
Define the population. Identify the total set of items (e.g., invoices, transactions, inventory records).
Determine the block size. Decide on the number of consecutive items to be tested (e.g., 50 or 100).
Select the starting point. Randomly choose a starting point within the population.
Examine the block. Test all items in the selected block for compliance or accuracy.
Block sampling is a better choice when transactions are processed in sequential order, in preliminary assessments where broad compliance is expected, or for internal control testing where systematic issues are unlikely.
Advantages and Disadvantages of Block Sampling
The main advantages of block sampling are that it is easy to implement and takes less time and effort than more complex sampling methods. However, the results of block sampling may not reflect the characteristics of the entire population. Also, it is susceptible to sampling bias due to clustering of similar items.
Example of Block Sampling
For example, an auditor elects to use block sampling to examine customer invoices, and intends to pick 50 invoices. She picks invoice numbers 1000 through 1049. As another example, the auditor decides to pick all invoices issued on April 15.
Haphazard Sampling
Under haphazard sampling, there is no structured approach to how items are selected. However, the person doing the selections will probably skew the selections (even if inadvertently), so the selections are not truly random.
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Personal Judgment
Under the personal judgment approach, the auditor uses her own judgment to select items, perhaps favoring items that have larger monetary values or which appear to have a higher level of risk associated with them.
Random Sampling
Under random sampling, a random number generator is used to make selections. This approach is the most theoretically correct, but can require more time to make selections.
Stratified Sampling
Under stratified sampling, the auditor splits the population into different sections (such as high value and low value) and then selects from each section.
Systematic Sampling
Under systematic sampling, selections are taken from the population at fixed intervals, such as every 20th item. This tends to be a relatively efficient sampling technique.