Use the following statistical sampling calculator to create your own risk-based compliance auditing plan by entering the appropriate population and reliability statistics in the designated fields. The required sample-size will be calculated automatically for each risk category. Learn more here.
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About Sampling Calculator
The above statistical sampling calculator uses the Cochran formula to calculate the sample size needed to measure the proportion of items in a large population with a specified level of reliability (confidence level) and precision (confidence limit).
Where p is the (estimated) proportion of the population that has the attribute in question, and q is 1 – p. Z is found in a Z Table for a selected confidence level, and e is the desired margin of precision i.e. margin of error.
# With compliance attribute sampling the audit result is always binary i.e. either an item is compliant or it is not; there is no grey area.
- The above calculator is only to be used for attribute sampling where the population is large and the results of the audit are expressed as a percent of the population i.e. percent compliance or non-compliance.
- When an audit result is obtained statistically it is possible to state with a stipulated degree of confidence that the collected statistic also applies proportionately to the unsampled portion of the population.
An audit conducted with a 95% confidence level returns a sample statistic of 25% with a confidence interval of 5%. On the basis of this result, it can be stated that there is a 95% probability (i.e. confidence level) that the true population parameter resides between 20% and 30%.