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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.
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
communication
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 actual copy of the standard to refer to
for auditing program purposes.
EBook
"Explanations and Definitions for ISO 19011:2002"
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