Systematic sampling

Systematic sampling involves the use of a rational approach to picking a sample from a population. The usual technique is to begin sampling at a random point in the population, and then make additional selections at a pre-determined interval. For example, if the decision is made to review 100 invoices in a population of 10,000 invoices, a systematic sampling approach would be to select every 100th invoice. Accordingly, the person conducting the review randomly decides to pick the 57th invoice (sorted by invoice number), followed by the 157th invoice, 257th invoice, 357th invoice, and so on. This approach can be inefficient, but ensures that a broad sample is selected that is likely to be relatively representative of the entire population. However, the sample may not be representative of the population if the list from which the sample was selected is organized in such a manner that the selections are not entirely random.