The third generally accepted standard of audit fieldwork requires that auditors obtain sufficient, competent audit evidence to afford a reasonable basis for an opinion regarding the financial statements under examination. In considering what constitutes sufficient, competent audit evidence, a distinction should be made between underlying accounting data and all corroborating information available to the auditor. What presumptions can be made about the following? The relative competence of evidence obtained from external and internal sources. The role of internal control with respect to internal evidence produced by a clients data processing system. The relative persuasiveness of auditor observation and recalculation evidence