Which of the following is a true statement regarding documentation requirements for analytical procedures?
　　a. When an analytical procedure is used during the overall review stage of the audit, the auditor is required to document the auditor's expectation and any additional procedures performed to investigate significant unexplained differences.
　　b. When an analytical procedure is used as the principal substantive test of a significant financial statement assertion, the auditor is required to document both the auditor's expectation and the factors considered in developing that expectation.
　　c. When an analytical procedure is used as the principal substantive test of a significant financial statement assertion, the auditor is required to document the reasons analytical procedures were performed instead of tests of details.
　　d. When an analytical procedure is used as the principal substantive test of a significant financial statement assertion, the auditor is required to document his or her expectation and management's concurrence with that expectation.
　　Explanation
　　Choice "b" is correct. When an analytical procedure is used as the principal substantive test of a significant financial statement assertion, the auditor is required to document both the auditor's expectation and the factors considered in developing that expectation.
　　Choice "c" is incorrect. There is no requirement that the auditor document the reasons analytical procedures were performed instead of tests of details.
　　Choice "d" is incorrect. There is no requirement that the auditor document management's concurrence with the expectation.
　　Choice "a" is incorrect. When an analytical procedure is performed during the overall review stage, there are no specific documentation requirements. The requirement that the auditor document the expectation and any additional procedures performed to investigate significant unexplained differences relates to analytical procedures performed as principal substantive tests.