Block selection may be used to check whether certain items have particular characteristics. For example an auditor may use a sample of 50 consecutive cheques to test whether cheques are signed by authorised signatories rather than picking 50 single cheques throughout the year. Block sampling may however produce samples that are not representative of the population as a whole,particularly if errors only occurred during a certain part of the period, and hence the errors found
cannot be projected onto the rest of the population.