top of page

The REAL odds of passing a Process Validation

Statistics tell us passing a PQ is not easy!

In validation we’re providing objective evidence the process is capable of successfully making the product consistently.

3 consecutive lots have typically been used to demonstrate this (although FDA does not specify a required number of lots and it is up to the manufacturer to justify.)

For key characteristics the capability is typically justified in statistical confidence and reliability. For example, 95% confidence / 97% reliability means we want to be 95% confident that greater than or equal to 97% of units made by the process meet the specification.

Although the statistical confidence & reliability apply to the manufacturing PROCESS, very often the sample size and acceptance criterion is applied per LOT. In that case, if 3 consecutive lots are made, what is the probability of passing the study?

Assuming an attribute quality characteristic and accept on zero failures criterion (a=0), the (binomial) probability of passing all 3 lots is shown in the figure below.

As can be seen, having a successful process validation is NOT easy!

To have a reasonable chance at passing the study, the actual process % defective must be MUCH LOWER (<1/20th) than would be indicated by the reliability!

Fortunately, there ARE ways of boosting the odds in our favor.

More in a future post...

Click to get your FREE PDF on the essentials of Medical Device process validation.


Related Posts

See All


New posts added regularly. To be among the first to know, subscribe.

bottom of page