Denise Robitaille  |  05/03/2009

Verification vs. Validation

You can verify and confirm, but that doesn’t mean it’s right.

As some of you know, quality “speak” and concepts have been known to bleed into my everyday life. This is not uncommon for quality professionals. The only difference between some of us and the rest of you is that many of you are still in denial. You won’t admit to the occasional slip of the quality tongue (e.g., “I need to see the objective evidence that you’ve done your homework.”)

Several years ago, a colleague from Central America asked if I had any good examples of the difference between verification and validation. This particular question has plagued many organizations for quite some time. How can something possibly be verified as meeting specification and still not be what the customer wants? It seems illogical, and yet the truth is that it can and does occur.

I told my friend that I did indeed have a good example and proceeded to tell him this true story:

I was helping my mother with some crafts for her church bazaar. My mother would crochet fancy attachments resembling a stylized pinafore that she would affix to kitchen towels. This not only made them very pretty, but served the practical function of creating a loop for hanging the towel.

My mother has a serious commitment to her church’s bazaar, and she’d committed to making several hundred of the towels. (My mother at the time was an octogenarian.) The crocheting could get tedious and the quantity grew daunting as the bazaar approached. I offered to help.

My mother had a pattern with very specific instructions that included the ply of the yarn and the gauge of the crochet hook. I gathered multiple skeins of yarn and headed home, where I spent much of my spare time during the next few weeks crocheting colorful mini-pinafores. I followed the instructions, using the specified hook and yarn. My little pinafores looked exactly like those that Mom made.

Unfortunately, when she attempted to sew my pinafores onto the towels, they were too small. The problem is that I crochet more tightly than my mom. An unanticipated and undefined process variation had resulted in a product that, although it met all the specifications in terms of number of stitches, number of rows, and gauge of tool, nevertheless was not fit for the intended use.

I thought to myself, “This is just like verification and validation.” (Yes, as nerdy as it sounds, I actually did say this to myself.) We had verified that the material, process, and tools were correct and that the output in terms of the defined instructions was also correct. I did exactly what my mother told me to do. However, when we moved on to validation, we found that despite verification of fulfillment of the defined requirements, the product still did not meet the intended need. They simply were not going to work.

In the same way, an organization can produce a product that is not what the customer intended or expected. This could be due to inadequate or ambiguous specifications. It could also result from variables in process or materials that have an adverse or unanticipated effect on the final output. Some of these might include:
A field installation estimate that didn’t take into account the cure time for the epoxy, resulting in a late completion
Shorter-than-expected shelf life of a product due to extreme temperatures
Negligible traces of a substance that was presumed to be inert and benign to the raw material
A software feature that functions properly but has a visual effect completely different than what the customer wanted

Some of these variables can probably be caught using several planning tools. Ensuring complete understanding of customer specifications, asking questions, and requiring more details can help mitigate these surprise outcomes. Processes like failure mode and effects analysis also serve to broaden individuals’ perspectives of potential problems.

However, even with robust processes in place and utilization of effective prevention tools, it’s still possible to have unanticipated consequences. That is what justifies the time spent on validation. It’s often the one last chance to catch a glitch that would otherwise get away from us.

In my mother’s case, she was able to alter the towels to fit the nonconforming pinafores. Your customers may not be quite so accommodating.

My friend thanked me for the story and asked permission to use it for training he was conducting in South America. I gladly granted consent and then let my mother know that there was a quality professional somewhere in Venezuela talking about her and her church bazaar towels.


About The Author

Denise Robitaille’s picture

Denise Robitaille

Authored of more than a dozen books on a variety of quality topicsDenise Robitaille has participated internationally in standards development for more than 20 years, serving in several leadership roles, including her current position as chair of TC176/SC1. That committee is responsible for the development of ISO 9000, the guiding document on quality fundamentals and terminology that is the foundation for ISO 9001.

Robitaille also chairs PC302, the committee responsible for revising the ISO 19011 standard on auditing quality management systems. She has facilitated the implementation of ISO 9001 for multiple organizations for more than 25 years, is a Fellow of the American Society for Quality, and a certified lead assessor.



I believe the comment below could be misleading, the way I've heard it is: Validation: are we designing the right product (to meet the customer's needs). Verification: are we designing the product right (meaning it meets our specs and design criteria).

Mnemonic..and the opposite..

Hi Denise,

Good story, thanks.  

I find this mnemonic helps with ISO 9001 terminology..

Verification = the answer to "have we designed the right thing?" - ie does it look like what the client wants?

Validation = the answer to "have we designed the thing right?" - ie does it work the way client wanted it to? 

That is, of course, until you come across a died in the wool, fully paid up, card-carrying food technologist who will tell you you have the defintions the wrong way round!