Crafting Effective Use Scenario Prompts: A Key to Medical Device Usability Test Success

In the course of planning a usability test, carefully selecting the tasks and use scenarios that participants will perform is among the most important steps you will take. That said, no matter how meticulously you have selected use scenarios, when it comes time to conduct testing, it all comes down to how you communicate your chosen use scenarios to test participants. This is where a usability test's use scenario prompts come into play, which the moderator might present to participants verbally or in written form. While crafting prompts that are clear and specific without being too verbose or directive can be a tricky balancing act, putting in the thought and effort to do so is key to a successful usability test. To help navigate the process of writing and refining prompts, keep the following tips in mind.

Set the scene–concisely

A prompt should help transport the participant out of the test room and into the mindset of actual product use. As such, it is important to set up the scenario with contextual details. You might present a setting (“You are at work…”), previous actions (“You just picked up your medication from the pharmacy…”), or the time of day (“It is time to have lunch…”) to add realism to a simulated use scenario.

That said, an overly elaborate prompt can make it hard for participants to stay attentive, remember the details presented, and identify the information on which they should take action to perform the use scenario. A one- to three-sentence prompt is usually sufficient to provide the necessary context and guidance for most use scenarios. 

Furthermore, details that are too specific can distract participants from the use scenario's intent. Consider the following prompt, intended to evaluate an insulin pump's “extended bolus” function: “You are about to eat pizza. Use your pump to deliver 10 units of insulin over two hours.” Mentioning pizza might help put participants in an actual pump use mindset. However, some participants might focus more on pizza than on the guidance provided in the prompt's second sentence. As a result, these participants might apply their usual insulin delivery approach for eating pizza (which might not be delivering an extended bolus) rather than following the prompt's guidance. Opening the prompt with more general context, such as “You are about to eat dinner,” would encourage participants to focus on the rest of the prompt for more specific guidance.

Describe what to do, not how to do it

To elicit participants' natural and unbiased interactions with a product, a prompt should present a goal or objective without describing how to get there. In most cases, a prompt should not directly point participants to any particular user interface features, nor should a prompt list the steps or subtasks involved in a use scenario.

Returning to the extended bolus example above, imagine the prompt instead stated, “Use your pump to deliver an extended bolus of 10 units of insulin over two hours.” In this case, because the prompt uses the exact language used in the device itself (i.e., “extended bolus”), the use scenario would fail to evaluate whether participants can identify the appropriate function for the insulin bolus specifications provided. In contrast, by excluding the function's name, the original prompt focuses on the use scenario’s objective of delivering a specified amount of insulin over a specified time rather than “giving away” a key step to achieving that objective.

Speak participants' language

It is important to consider who your participants are and select use scenario prompt language accordingly. For layperson participants, avoid using technical jargon, and if your study includes children, seek opportunities to further simplify prompt wording. Doing so helps make participants feel comfortable while also ensuring the prompt's intent is effectively communicated.

On the other hand, when working with clinicians or other technical professionals, you should make sure that prompts include the appropriate technical terminology and use correct syntax. Using language that matches how participants converse in their professional environments helps the participants to feel more like they are completing tasks at work rather than within a simulated scenario, thereby adding realism to the test.

Conclusion

A usability test’s success hinges on effective communication between the test team and the participants, and for this reason, strong use scenario prompts are key. Taking the time to craft and refine clear and concise prompts that convey realistic scenarios and are tailored to participants’ backgrounds will help facilitate a productive and fulfilling usability test.

Hannah Miller is Human Factors Specialist at Emergo by UL’s Human Factors Research & Design division.

Additional human factors engineering (HFE) and usability resources:

• Human factors design and prototype development support
• HFE user research for medical devices, IVDs and combination products