Design Verification and Validation

I’ve often been asked what the difference is between design verification and validation.  The terms design verification and design validations seem to mean the same thing, and in some standards the terms verification and validation are used interchangeably.  In ISO 9001, they are used to mean different things.

When and engineer starts a design, he starts with design inputs – the requirements he’s designing to.  When the design is complete, there are design outputs: specifications, drawings, etc. that describe the design.  Design verification then is the step of verifying that all the design input requirements have been addressed in the design.

A technique I like to use to do design verification is a compliance matrix.  Each row of the matrix is an input requirement, and each column of the matrix is a design output specification section or paragraph.  In a cell where the input was addressed in a particular specification I place an ‘X’ to indicate that the input requirement is addressed there.

To imagine the compliance matrix, consider an Excel spreadsheet where the requirements are the numbered rows, and the design output that addresses the requirement is one of the lettered columns.  In most cases one input requirement is addressed in one place in the output specifications, but this is not necessarily the case.   I’ve used this technique when assisting customers in the design of a quality management system based on ISO 9001.

Design validation is the process of determining whether or not the design functions to the input specifications.  This means manufacturing the product to the specifications and testing it against the input and output requirements to see if it works as intended.  Prototype testing falls into this category.  A test plan is created based on the input and design requirements (there might be additional requirements required by the design that were not included by the customer), and the product is tested to determine conformance.