Audit Sampling Flashcards
What is audit sampling?
The application of a procedure to less than 100% of a population to draw a conclusion about the whole
What is attribute sampling?
Analyzes a sample to see how often a given attribute appears and extrapolates it to the whole population
Generally used for tests of controls – looks at several occurrences and counts how many times an occurrence deviates from the design
What is variable sampling?
Analyzes a sample to compute some particular variable for the whole, such as standard deviation
Generally used for substantive tests on transactions and account balances
What is dual-purpose sampling?
Combination of attribute sampling and variable sampling
What are some conditions for using dual-purpose sampling?
(1) The auditor should use it only if there’s a low risk that the deviation rate in the population exceeds the tolerable rate
(2) The sample size should be the greater of whatever sample sizes would have been chosen if the sampling methods were done individually
Is sampling always an acceptable way to reduce audit risk?
Nearly always – sometimes the risk is so high that all data must be examined
What are two components of audit risk?
(1) Sampling risk - risk that the conclusions drawn from the sample will falsely represent the whole population
(2) Nonsampling risk - all other possible risks (e.g. from poor planning, oversight, neglect)
For tests of controls, what are two different aspects of sampling risk?
The risk of assessing the control risk (based off the sample) as either (1) too high or (2) too low
For substantive tests, what are two different aspects of sampling risk?
(1) Risk of incorrect acceptance (beta risk) - when the sample implies that a population is not misstated when it is
(2) Risk of incorrect rejection (alpha risk) - when the sample implies that the population is misstated when it is not
If samples lead the auditor to conclude a higher risk than warranted, how does it hurt the audit?
It hurts the EFFICIENCY of the audit, since the auditor will do more work than necessary to overcome the calculated risk
If samples lead the auditor to conclude a lower risk than warranted, how does it hurt the audit?
It hurts the EFFECTIVENESS of the audit, because the auditor will not do as much testing as is needed to arrive at a stable conclusion
What are common procedures for collecting samples?
Haphazard sampling Random sampling Systematic sampling Stratified sampling Block sampling Probability-proportional-to-size sampling
What is haphazard sampling?
Completely unsystematic sampling, neither purposely random nor nonrandomly systematic
However, it is not simply careless – it just includes professional (unbiased) judgments
Can haphazard sampling be used for statistical sampling?
No, it is always nonstatistical
What is random sampling?
The use of random numbers (e.g. as generated by a computer or taken from a table) to accumulate a sample
Can be done with replacement (putting back an item in the population after selecting it) or without replacement
-without replacement is more common
What is systematic sampling?
Collecting a sample with a definite interval between each item selected (e.g. selecting every 7th item from a random starting point)
How is the interval determined for systematic sampling?
There is usually a uniform interval, calculated as (population size) / (sample size)
What is stratified sampling?
Sampling which first breaks apart the population into various strata (or clusters) and then treats each stratum separately
E.g. dividing accounts into (1) less than $1000, (2) between $1000 and $3000, and (3) greater than $3000, then treating them differently
What is the mean-per-unit (MPU) method?
A method which takes the mean of a sample and multiplies it by the total population to project the total value of the population
How does the MPU method benefit from stratified sampling?
By breaking up a population into homogeneous strata, the auditor can get a sample that is sure to adequately represent the range of values in the population – and thus the mean of the sample will better reflect the mean of the population
Stratified MPU is therefore more efficient
What is block sampling?
Sampling which takes a particular “block” of the population (e.g. all invoices from March, or check numbers 250-299)
When is it good or bad to use block sampling?
Bad for statistical sampling purposes
Good when trying to measure the effect of some control change, looking at the block of data around that date
Does sampling apply to risk assessment procedures done on internal control?
No
What is the tolerable rate of deviations for tests of controls?
The maximum rate of deviations in an internal control that would support the auditor’s assessed level of control risk
-if the error rate is higher, then the assessed level of control risk increases too
What is allowable risk for tests of controls?
Sampling risk is the risk of assessing control risk to be too low, so allowable risk is whatever sampling risk the auditor allows
Allowable risk is inversely related to the desired degree of assurance which the auditor wants from the sample – if he wants a high degree of assurance, he should allow less sampling risk
What is allowable risk for substantive tests?
The risk, allowed by the auditor, of incorrect acceptance
What is the tolerable misstatement for substantive tests?
The maximum amount an account balance can be misstated – above which, when combined with possible misstatements from other accounts, there would be a material misstatement for the financials as a whole
What is the main difference between statistical and nonstatistical sampling?
Statistical sampling allows uncertainty to be quantified (i.e. the measurement of sampling risk)
Risks are included in nonstatistical sampling only as professional judgments, not strict numbers
Can nonstatistical sampling provide appropriate and sufficient audit evidence?
Despite that it cannot quantify sampling risk, yes
What is the primary reason to choose statistical or nonstatistical sampling?
Costs vs. benefits
Statistical sampling takes more time to design and implement
What are some different methods for doing attribute sampling?
(1) Sequential sampling
(2) Attribute estimation method
(3) Acceptance sampling method
(4) Discovery sampling method
What is sequential sampling?
A methodical procedure where each step depends on the previous one
What is the attribute estimation method?
A method where a sample is selected and error rate is extrapolated to the whole population
What is the acceptance sampling method?
A particular kind of attribute estimation method
Involves a table which takes the population size, sample size, and number of sample errors to determine a given % confidence that the population error rate does not exceed a particular %
What is the discovery sampling method?
A particular kind of acceptance sampling method
Determines how large a sample needs to be in order to have a % confidence that, if the population error rate is at least X%, the sample will have an error
-Then, if there is no error, the auditor can conclude a maximum error rate of X%
When is discovery sampling typically used?
When the auditor expects a very low error rate, and when there is some special problem (e.g. possible forgery)