Section: Volume A

Stratified sampling is used when the population can be divided into distinct subgroups (strata) that differ significantly from each other but are internally homogeneous. In the context of auditing, revenue earned through cash receipts or as receivables would have different characteristics and risk profiles. Stratifying the population allows the auditor to ensure that each subgroup is adequately represented in the sample, leading to more reliable and accurate audit conclusions.
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The Institute of Internal Auditors (IIA) Practice Guide: Audit Sampling IIA Standard 2320 - Analysis and Evaluation

When using the balanced scorecard approach to assess the performance of the internal audit activity, a key performance indicator relevant to the audit client is the percentage of recommendations implemented by the corrective action date. This KPI measures the effectiveness and impact of the audit activity by tracking how well the audit recommendations are being acted upon within the agreed-upon timeframe. It reflects the responsiveness and commitment of the organization to address identified issues and improve its control environment, which is directly relevant to the interests and concerns of the audit clients.
Reference:
The Institute of Internal Auditors (IIA) Practice Guide: "Measuring Internal Audit Performance" Kaplan, R.S. & Norton, D.P. (1996). "The Balanced Scorecard: Translating Strategy into Action"