The use of statistic for activities related to quality management System is of great importance and both ISO 13485 and FDA regulation have specific requirements. This is done to ensure to have reliable data in relation to sampling, either for incoming inspections, for verification and validation activities or data analysis.

FDA Quality System Regulation has a specific section related to statistical methods, ref. 21 CFR 820.250. Specifically, two well defined requirements are mentioned:

(a) Where appropriate, each manufacturer shall establish and maintain procedures for identifying valid statistical techniques required for establishing, controlling, and verifying the acceptability of process capability and product characteristics. 

(b) Sampling plans, when used, shall be written and based on a valid statistical rationale. Each manufacturer shall establish and maintain procedures to ensure that sampling methods are adequate for their intended use and to ensure that when changes occur the sampling plans are reviewed. These activities shall be documented.

The first requirement is related in having a specific procedure to identify the appropriate statistical methods when it needs to be used, such us for verifying product characteristics or process capability.

The second requirements is specifically related to sampling plan. It requires that, when sampling plans are used, they shall be based on a valid statistical rationale. Moreover, the sampling shall be adequate to their intended use and modified if changes occur. In this framework, it is possible to envision the use of a risk-based approach to ensure that sampling.

There are specific statistic-related requirements as well in ISO 13485:2016. First, in section 7.3.6 and 7.3.7, related to design verification and validation, it is mentioned:

The organization shall document verification (validation) plans that include methods, acceptance criteria and, as appropriate, statistical techniques with rationale for sample size.

So, it is necessary to justify the sample size used for activities of verification and validation through specific statistical technique.

In section 7.5.6, related to validation of processes for production and service provision, it is reported, at point d), that in procedure for validation activities statistical technique with rational for sample size shall be documented.

Moreover, in section 8.1 related to KPI to keep processes under control, it is reported that in planning and implementation of activities related to monitor, measure, analyse and improve processes, the “determination of appropriate methods, including statistical techniques, and the extent of their use” shall be documented.

Finally, in section 8.4 related to Analysis of Data, it is again reported that the procedure for data analysis “shall include determination of appropriate methods, including statistical techniques and the extent of their use”.

As it has been discussed above, statistic became of fundamental importance in Quality Management System. The use of statistic has been included within different quality requirements for ISO 13485:2016 standards and FDA QSR regulation.

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