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 client's data processing system.

· The relative persuasiveness of auditor observation and recalculation evidence