Acca aa s21 Notes

Haphazard selection.
This is frequently used because it is convenient. For example, the auditor 
opening a file at random and picking the invoice at which the file is opened. There can be 
obvious problems with this. The file might always open at a slightly thicker invoice or a slightly 
larger invoice and that invoice could be from the same small group of suppliers. There might be 
a relatively small chance of the physically small invoice being chosen. There is also a risk of bias. 
The auditor may, consciously or unconsciously pick out invoices which appear to be correct (so 
quickly dealt with) or 'more interesting' (perhaps more likely to have an error). The sample is 
therefore unlikely to be representative, so cannot be used in statistical sampling.
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Block selection.
For example choosing 20 invoices all in a sequence. Depending on how they 
are filed, they could all from the same supplier or may be from different suppliers, but all with 
the same date. This is not a representative sample. (Clearly it would not be possible in a test of 
control to conclude on the effectiveness of controls throughout the period.) 
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Stratification.
If we know that there are 20,000 invoices, 10 of those are above 100,000 then it 
might make sense to make sure we choose at least all of those 10 invoices plus another 10 
chosen randomly. Stratification means dividing your population into different sub-populations 
('layers') with similar characteristics (usually monetary amount). The results of testing each layer 
must be separately evaluated.
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Value-weighted selection.
This is used in monetary unit sampling and is rather more complex 
as described on the next page.
September 2021 to June 2022 exams
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