Final answer:
Auditors typically consider documentary evidence from independent external sources as the most appropriate, with direct personal knowledge through observation and recalculation also being important, while internal documents and executive representations are considered with caution due to potential for bias.
Step-by-step explanation:
The evidence considered most appropriate by auditors is generally documentary evidence obtained directly from independent external sources. This type of evidence is preferred because it is less likely to be influenced by the entity being audited and is considered more reliable. However, auditors also value direct personal knowledge obtained through physical observation and mathematical recalculation, as well as internal documents like sales invoice copies, especially when they are produced under conditions of strong internal control. Written representations made by the president of the entity can be useful, but they are considered weaker evidence due to the potential for bias.