Audit Sampling Flashcards
Confidence Level
The sample’s confidence level refers to the reliability the auditor places on the sample results. Confidence levels of 90 percent to 99 percent are common. A 95 percent confidence level means the auditor assumes the risk that five out of 100 samples will not reflect the true values in the population. The auditor’s assessment of the control environment contributes to the level of risk the auditor is willing to assume. At a 95 percent confidence level, 5 percent the complement of the confidence level reflects the auditor’s risk of “assessing control risk too low.”
Expected Deviation Rate
The expected deviation rate represents the auditor’s best estimate of the actual failure rate of a control in a population. The rate usually is based on client inquiries, changes in personnel, process observations, prior year test results, or even the results of a preliminary sample.
Tolerable Rate
The tolerable rate defines the maximum rate of noncompliance the internal auditor will “tolerate” and still rely on the prescribed control. Many auditors will coordinate with their audit client before establishing a tolerable level. Client control objectives help determine the nature and frequency of deviations that can occur and still allow reliance on the control.
Population
The population contains all items to be considered for testing. Each must have an unbiased chance of selection to ensure the final sample is representative of the population. For large populations containing thousands of items, population size will cause little impact on total sample size and is often irrelevant for audit sample planning.
Define “block sampling.” (least desirable)
Sampling methodology where a group of contiguous items are selected; (e.g., selecting all transaction for the month of June).
Define “haphazard sampling.”
Sampling methodology where items are selected arbitrarily with no conscious biases.
Define “systematic sampling.”
Sampling methodology whereby every nth item in the population is chosen as part of the sample (usually with a random starting point).
List the eight steps in attributes sampling plan.
1-Define what Constitutes an Occurrence, 2-Identify Relevant Population, 3-Determine Sampling Method, 4-Determine Sample Size, 5-Select the Sample, 6- Evaluate Results, 7- Document Sampling Procedures.
List the two sampling approaches acceptable for statistical sampling applications
Random ans Systematic
Define “random sampling.”
Sampling methodology where each item in the population has the same probability of being selected.
List the three factors, as indicated by AICPA tables, that determine sample size for an attributes sampling application.
1-Expected error rate (related to the variation in population)
2-Tolerable error rate (related to precision) and
3-Risk of over-reliance (Type II error rate).
List the factors that directly relate to sample size.
Expected error rate, Population size - not explicitly considered in attributes sampling.
What is the formula for the observed deviation rate for the sample?
(# errors in the sample)/sample size
List the factors that are inversely related to sample size.
Tolerable error rate, Risk of over-reliance - Type II error, Risk of under-reliance.
List the two sampling approaches normally associated with judgmental (nonstatistical) sampling applications.
Block, haphazard
List the items that are directly related to sample size in variables sampling
Estimated population standard deviation, Population size - considered explicitly in variables sampling.
What is the basic sample size formula?
Sample Size = (Estimated population standard deviation x coefficient of reliability x population size / allowance for sampling risk) squared
List the items that are inversely related to sample size in variables sampling.
Allowance for sampling risk. Risk of incorrect acceptance (Type II error). Risk of incorrect rejection (Type I error)
What is the purpose of stratification?
To reduce the overall variability within a population.
What is the formula to obtain the sample size for Probability Proportionate to Size (PPS) sampling?
n = reliability factor (from PPS tables) x Book Value / tolerable error