Does anyone inspect the expiration date on the package?

Probably not but maybe? The only time I check the expiration date is when I open the fridge and see something that's been there for a long while. But I don't deliver healthcare and thankfully, healthcare practitioners are a bit more conscious than I am.

The purpose of an expiration date is to indicate the period during which the product is expected to remain stable and retain its identity, strength, quality, and purity when stored under the labeled storage conditions. For more information (https://www.fda.gov/drugs/pharmaceutical-quality-resources/expiration-dates-questions-and-answers). For some medical devices, the expiration date may be critical information that could impact the overall safety and efficacy of device use.

The task of inspecting the expiration date and/or the packaging is in nearly all HFE summative/validation studies, most often as a critical task. In most cases, this task is a knowledge task; however, in some instances, it may be observed, but the behavior is over in a flash. This becomes a challenge in human factors validation studies. Should you make this a knowledge task? How will you ask the cascade of questions that gently guide a study participant to communicate their knowledge of the expiration date? If asked directly, of course, they will say they look at it. Should you make this an observed task? How will you know they really looked at it unless the participant took the time to study it? If they didn't study it, how will you confirm that the task of checking the expiration is complete? What if you make it both an observed task and a knowledge task? In this instance, you may not observe the task, which is a use error; however, in the knowledge task, they likely knew they needed to do it or would communicate that it was simply a test artifact- that they routinely complete this task in the clinic, but since this is a study, they didn't feel it was necessary.

I wish I had a simple answer on best practice. I don't. Other than yes, if it's a critical task, it should be evaluated in the validation study. The method observation vs knowledge task is really a matter of context and the clinical risk associated with the critical task. If a task is readily observable, let that be your first choice. If not, knowledge tasks are always there as an option. Personally, choosing both poses a challenge in the event that one is a use error and the other a success. This requires more explanation, which would make your report longer without adding much value.

Expiration date checking, as a critical task, will always be tricky. Pick an evaluation method; if there is a use error or a suspected one, be sure to ask subjective questions before you leave the interview. This can go a long way toward demonstrating a safe and effective user interface.