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Chapter 10. Audit Sampling. Introduction. Overview of Audit Sampling Definition Population Nonsampling and Sampling Risk Assessing control risk to high Assessing control risk to low. Sampling Risk: Substantive Testing. Risk of incorrect acceptance Risk of incorrect rejection
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Chapter 10 Audit Sampling
Introduction Overview of Audit Sampling Definition Population Nonsampling and Sampling Risk Assessing control risk to high Assessing control risk to low
Sampling Risk: Substantive Testing • Risk of incorrect acceptance • Risk of incorrect rejection • Selecting a Sampling Approach • Statistical sampling • Nonstatistical sampling • Sampling to Test Controls • Attribute estimation sampling
Substantive Sampling Considerations • Basic Steps: • Specify audit objective • Define a misstatement • Define the population • Choose sampling method • Determine sample size • Selectthe sample • Audit the selected items • Evaluatethe sample results • Perform follow-up work as necessary • Document
Specify the Audit Objective • Combination of sampling and other audit procedures. • Sampling used in two ways: • Determine reasonableness of an account balance. • Estimate some amount.
Define Misstatements • Misstatements should be defined before beginning to: • preclude rationalizing away misstatements • provide guidance to the audit team • Misstatement: a difference that affects the correctness of the overall account balance.
Define the Population • Group of items in an account balance that the auditor wants to test. • Does not include: • items that the auditor has decided to examine 100%. • items that will be tested separately.
Define the Sampling Unit • Sampling units are the individual auditable elements as defined by the auditor. • Completeness of the Population • Auditor needs assurance that the list accurately represents the population.
Identify Individually Significant Items • Top stratum--few large-dollar items • Lower stratum--the remaining items • Stratification of the population
Choose a Sampling Method • Nonstatistical • Probability proportional to size (PPS) • Classical sampling methods (Appendix 10B) • Mean-per-unit • Ratio estimation • Difference estimation
Determine the Sample Size, Select the Sample, and Evaluate the Results • Tolerable misstatement • Expected misstatement • Document the Results
Nonstatistical Sampling • Determine sample size • Selecting the Sample • Haphazard selection • Evaluating the sample results • Using audit software
Probability Proportional to Size Sampling • PPS sampling is an adaptation of attribute sampling methods to dollar value testing. • Population definition • Test of details risk (incorrect acceptance) • Other substantive procedures risk (OSPR) • Sample size and selection • Zero and Negative Balances
PPS • Sample Evaluation • Error Evaluation Terminology • Upper misstatement limit (UML) • Basic precision • Most likely misstatement (MLM) • Incremental allowance for sampling error • Allowance for sampling error
Appendix 10A: Sampling to Test Controls • Planning Factors • Audit objective • Tolerable failure rate • Expected failure rate • Allowance for sampling error (precision) • Allowable risk of assessing control risk too low
Sampling to Test Controls • Nonstatistical sampling • Attribute Estimation sampling • Define the attributes of interest and failures • Define the population • Period covered by the tests • Sampling unit • Ensuring the population is complete
Sampling to Test Controls • Determine the Sample Size • Multiple attributes • Effect of population size (finite adj. factor) • Determine the method of selecting the sample • Random numbers • Systematic selection • Haphazard selection
Sampling to Test Controls • Select and audit the sample items. • Evaluate the sample results. • Quantitative evaluation • Qualitative evaluation • Linkage to substantive testing
Appendix 10B: Classical Sampling Methods • MPU Sampling • Difference estimation sampling • Ratio estimation sampling • Sample Size • Estimation of population standard deviation • Desired allowance for sampling error
Classical Sampling Methods • Sample Selection • Sample Evaluation • Point estimate • Projected misstatement • Achieved precision • Decision rules • Adjusted achieved precision • Unacceptable results
Classical Sampling Methods • Comparison of PPS and classical sampling • Computer support