- audit population
means a sampling population composed of units with positive values where expenditure is above 0;
- bilateral testing
means an approach to statistical sampling allowing the calculation of both the upper error limit and the lower error limit;
- confidence interval
means the interval that contains the true value of error in the population with a certain probability known as ‘confidence level’;
- confidence level
means a probability that a confidence interval includes the true value of the estimated parameter;
- equal probability
means one of the random selection methods in which random numbers are used in order to select randomly the units constituting the sample with equal probabilities;
- exhaustive stratum
means a part of the positive population related to the accounting year or to a sampling period for which all sampling units are audited.
- lower error limit
means an error limit calculated by deduction of the ‘sampling precision’ from the ‘extrapolated error’, adjusted, where applicable, by adding delimited systemic errors and uncorrected anomalous errors;
- multi-period sampling
means a sampling procedure where the audit population for an accounting year is divided into two or more sampling periods, which could be of the same or of a different length;
- negative population
means a sampling population composed of units with negative values or null values where expenditure is below or equal to 0;
- non-statistical sampling method
means a sampling method that does not involve the evaluation of the sampling risk and precision and is based on a random selection;
- PPS
means one of the random selection methods that uses the monetary unit as an auxiliary variable for sampling where the selection of the units constituting the sample is based on a probability proportional to the monetary value of the sampling unit (higher value units have higher probability of selection) and the selection is usually based on a systematic selection with a random starting point and application of a systematic rule to select the additional units;
- projected error
means the result of extrapolating the random errors found in the sample to the total population where the extrapolation/projection procedure depends on the sampling method used;
- random selection
means a probabilistic selection which refers either to probability proportional to size or equal probability selection ensured by using random number generating software, specialised or not, including MS Excel;
- sampling method
means a technical tool to select a sample and extrapolate results within a sampling methodology, which may be either statistical or non-statistical;
- sampling methodology
means a methodology describing the main elements and steps of a sampling procedure and which encompasses a sample selection stage including subsampling and extrapolation of results;
- sampling precision
means a sampling parameter measuring uncertainty in the extrapolation of sampling results to the population, and corresponding to the maximum expected deviation between the extrapolated error and the true population error which is achieved with a probability equal to the confidence level;
- SRS
means a standardised statistical sampling method based on equal probability selection, compatible with different sampling designs, including stratification and ‘multi-period sampling’;
- subsampling
means a two-stage or multi-stage sampling where an error for a sampling unit is established on the basis of an extrapolation from a subsample of invoices or other subsampling units;
- subsampling unit
means a unit, which may be an invoice or other unit, into which a sampling unit is divided for the purpose of subsampling and which is audited exhaustively unless another level of subsampling for the subsampling unit is applied;
- unilateral testing
means an approach to statistical sampling allowing the calculation of only one error limit, typically the upper error limit;
- upper error limit
means the sum of the ‘sampling precision’ and the ‘extrapolated error’ and, where applicable, delimited systemic errors and uncorrected anomalous errors;