ISO 19011 - Section 13
Explanations in Plain English
ISO 19011 - Section 13 - Sampling
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.
More in depth discussions are included in the ebook below.
The links below are
excerpts from the our e-book
"Explanations and
Definitions for ISO 19011:2002" 
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 a copy of our ebook to refer to when auditing.
EBook "Explanations and Definitions for ISO 19011:2002
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