As a result of tests of controls, an auditor assessed control
risk too low and decreased substantive testing. This assessment
occurred because the true deviation rate in the population was

(d) The requirement is to identify the circumstance that
would cause an auditor to assess control risk too low and
decrease substantive testing inappropriately. Answer (d) is
correct because when the true deviation rate in the population
exceeds that in the sample, the auditor may assess control risk too
low. The AICPA Audit Sampling Guide discusses tests of controls
and attributes sampling in its second chapter. Answers (a)
and (c) are incorrect because the true deviation rate and the risk
of assessing control risk too low do not have such a relationship,
either positive or negative. Answer (b) is incorrect because a
deviation rate in the population that is less than the deviation rate
in the auditor’s sample may lead the auditor to assess control risk
too high.