Section 13 - ISO 19011

Sampling - ISO 19011 - Section 13

The definition of sampling is:

the act, process or technique of selecting a suitable sample; specifically: the act, process or technique of selecting a representative part of a population for the purpose of determining parameters or characteristics of the whole population. For audits it is a technique used in order to collect sufficient objective evidence to determine whether a process or system is in compliance or has nonconformities to the standard.

Examples of a sampling population for an audit are members of an auditee’s organization, or records to review,

Looking at all the records or interviewing every employee is very often not possible because of time and resource constraints on the audit team. Therefore, representative samples of employees are interviewed and representative samples of records are reviewed. 

The sample size selection is very subjective:

The following guidelines are recommended.

- Take an initial random sample of 15 -25% of the records you need to review. Use lower sample sizes when the number of records is larger.

- If the records are generated primarily through an automated computer process, a smaller sample size is acceptable. Chances are if the sample you review is conforming the remainder of the population generated by the system is also okay. The same holds true if the sample is nonconforming.

- If the records show objective evidence of compliance, you can make the observation that you have objective evidence of compliance. Document a description of the sample you reviewed. If possible, initial the records in an inconspicuous place.

- If the initial sample shows objective evidence of noncompliance, take an additional 10 – 15% random sample to determine the severity of the nonconformity.

For the number of employees to interview/audit, the same percentage sampling guidelines can be applied. 

Section 1. ISO 19011 Scope reference and definitions

    Section 2. ISO 19011 Principles of auditing

    Section 3. ISO 19011 Managing an audit program

    Section 4. ISO 19011 Audit program implementation

    Section 5. ISO 19011 Audit activities

    Section 6. ISO 19011 Preparing for onsite activities

    Section 7. ISO 19011 Conducting onsite activities

    Section 8. ISO 19011 What the auditor is looking for

    Section 9  ISO 19011 Audit reporting

    Section 10. ISO 19011 Audit techniques

    Section 11. ISO 19011 Audit path

    Section 12. ISO 19011 Effective communications

    Section 13. ISO 19011 Sampling

    Section 14. ISO 19011 Audit completion and follow-up

    Section 15. ISO 19011 Competence and evaluation of auditors

This represents a summary of the section in ISO 19011:2002. It's suggested that you obtain an copy of "ISO 19011 Explanations and Definitions".