Kế toán, kiểm toán - Chapter 9: Audit sampling

Audit SamplingChapter 9What is Audit Sampling? Applying a procedure to less than 100% of a populationTo estimate some characteristic of the populationQualitativeQuantitative 2Advantages of Statistical SamplingDesign efficient samplesMeasure sufficiency of evidenceObjectively evaluate sample results3Selection of Random SampleRandom number tablesRandom number generatorsSystematic selection4Random Number Table5Types of Statistical Sampling PlansAttributes samplingDiscovery samplingClassical variables samplingProbability-proportional-to-size sampling6 Requirements of AuditSampling PlansWhen planning the sample consider:The relationship of the sample to the relevant audit objectiveMateriality or the maximum tolerable misstatement or deviation rateAllowable sampling riskCharacteristics of the populationSelect sample items in such a manner that they can be expected to be representative of the populationSample results should be projected to the populationItems that cannot be audited should be treated as misstatements or deviations in evaluating the sample resultsNature and cause of misstatements or deviations should be evaluated7 True State of Population Deviation Rate Deviation Rate Exceeds Is Less ThanAuditors’ Conclusion Tolerable Rate Tolerable RateFrom the Sample Is: Deviation Rate Exceeds Tolerable Rate Deviation Rate Is Less Than Tolerable Rate Sampling Risks--Tests of ControlsCorrectDecisionIncorrect Decision (Risk of Assessing Control Risk Too High)IncorrectDecision(Risk of AssessingControl RiskToo Low)Correct Decision8 Audit Sampling for Tests of ControlsDetermine the objective of the testDefine the attributes and deviation conditionsDefine the population to be sampledChoose an audit sampling techniqueSpecify:The risk of assessing control risk too lowThe tolerable deviation rateEstimate the population deviation rateDetermine the sample sizeSelect the sampleTest the sample itemsEvaluate the sample resultsDocument the sampling procedure9Sampling Risks--Substantive Tests True State of Population Misstatement in Misstatement in Account Exceeds Account Is Less Auditors’ Conclusion Tolerable Amount Than Tolerable From the Sample Is: AmountMisstatement inAccount Exceeds Tolerable AmountMisstatement inAccount Is LessThan TolerableAmount CorrectDecisionIncorrect Decision (Risk of Incorrect Rejection)IncorrectDecision(Risk of Incorrect Acceptance)Correct Decision10Audit Sampling for Substantive TestsDetermine the objective of the testDefine the population and sampling unitChoose an audit sampling techniqueDetermine the sample sizeSelect the sampleTest the sample itemsEvaluate the sample resultsDocument the sampling procedure11Population Variability—Why it MattersItem Population A Population B 1 2,100 8,000 2 2,100 25 3 2,100 2,000 4 2,100 400 5 2,100 75Mean 2,100 2,100Standarddeviation -0- 3,395 The variability determines how much information each of the items in the population tells you about the other items in the population. 12Factors Affecting Sample Size13Determining Sample Size--MPUSample size = 14Determining Sample Size--MPU SamplingPlanned allowancefor sampling risk = Tolerable misstatement______________________ 1 + Incorrect acceptance coef. Incorrect rejection coef.15Adjusted allowance for sampling risk = Tolerable _ (Population size * Incorrect acceptance coef. * Sample stan. dev.) misstatement Sample size This formula “adjusts” the allowance for sampling risk to consider the standard deviation of the audited values in the sample. It holds the risk of incorrect acceptance at its planned level.Variables Sampling Illustration--MPU 16 Variables Sampling Illustration--MPUUsing the text example with a standard deviation of audited values of $16Adjusted allowance for sampling risk = Tolerable _ (Population size * Incorrect acceptance coef. * Sample stan. dev.) misstatement Sample size = $364,000 _ ($100,000 * 1.64 * $16) 225 = $189,067We would still “accept” the book balance because the $6,250,000 (book value) falls within this intervalEstimate of total + Adjusted allowanceaudited value for sampling risk $6,100,000 + $189,067 [$5,910,933 to $6,289,067]17Acceptance Interval18Nonstatistical Variables Sampling IllustrationPlan Sample:Population: Size = 363 itemsBook value = $200,000Tolerable misstatement = $10,000Risk assessments:Inherent and control risk = Slightly below maximumOther substantive tests = Moderate19Nonstatistical Sampling--Determination of Sample SizeSample size = Population book value X Reliability factor Tolerable misstatement = $200,000 X 2.0 = 40 items $10,000 20Nonstatistical Sampling--Evaluation of Sample ResultsSample results: 40 accounts in sample $350 net overstatement $60,000 book value of sample items Projected misstatement: = [Sample net misstatement] X Book value of population [ Book value of sample ] = [ $350 ] X $200,000 [$60,000] = $1,167 Since the projected misstatement is only 11.7 percent ($1,167/$10,000) of tolerable misstatement, it is likely that the auditors would conclude that the account balance is materially correct. 21PPS Sampling IllustrationPopulation book value = $6,250,000Other Information:Tolerable misstatement = $364,000Sampling risk--Incorrect acceptance = 5%Expected misstatement = $50,000Use Figures 9-14 and 9-15 to obtain a “reliability factor” and an “expansion factor.”22PPS Sample Size ComputationSample size = Recorded amount of population * Reliability factor Tolerable misstatement - (Expected misstatement * Expansion factor)= $6,250,000 * 3.0 = 66 $364,000 - ($50,000 * 1.6) Sampling interval = Book value of the population Sample size = $6,250,000 = $95,000 (approximately) 66 23PPS Evaluation of ResultsUpper Limit on misstatement = Projected misstatement + Basic precision (Rel. factor x interval) + Incremental allowance24Calculation of Upper Limit on Misstatement25