Simulated use and real use studies

Terms and context

The distinction between simulated and actual use describes the conditions under which users operate a medical device in a usability study. In simulated use, participants operate the device in realistic use scenarios, but under simulated conditions. The FDA gives examples such as a device that is not switched on, or use on a manikin instead of a patient. Real use (in the guidance: “actual use”), by contrast, means that the device is used under the actual conditions and in the actual environment. The FDA describes the use environment as the actual conditions and setting in which users interact with the device.

The terms come from the FDA human factors guidance in the version of August 3, 2026 (as of November 2026). “Real use” is not a fixed term there; the guidance speaks of “actual use”, and this article uses both as synonyms. The guidance contains non-binding recommendations.

Simulated use: setting and realism

Simulated use studies take place in a recreated environment, for example in a study room or a simulated treatment situation. The FDA uses them in two phases. In the formative evaluation, they provide early data and can be adapted flexibly to the question at hand. In addition, the guidance considers simulated use testing necessary because analytical methods do not involve real users, and use errors often surprise analysts.

For validation, the guidance sets specific requirements for the simulation:

• Realism: The conditions should be realistic enough that the results can be transferred to actual use. How much realism is needed depends on the risk analysis of the purpose, users, use environment and user interface.
• Use environment factors: Environmental influences that can affect the interaction belong in the simulation. The guidance names dimmed lighting, several simultaneous alarms, distractions and multitasking.
• Independent use: Participants should use the device as independently and naturally as possible, without influence from the test moderator. The think-aloud method is not acceptable in validation because it does not reflect actual use behavior.
• Sources of information: If users have the instructions for use available in practice, they should also be available in the test, without participants being told to use them. A telephone hotline may be offered realistically, but the person providing information is not in the room and does not guide participants through the tasks.
• Training: The participants’ training should match the training of the actual users. According to the guidance, a test after different training is not valid, and time should pass between training and test because what was learned fades.

Real use: actual use and clinical study

For real use, the guidance distinguishes two variants. The first is a human factors test under actual conditions (“actual-use testing”). In principle, it follows the same guidelines as the simulated use test: Participants should represent the actual users (see representative users), the clinical environments should correspond to the actual use environments, and the procedure should influence the interaction as little as possible. If the requirements of 21 CFR Part 812 apply in the US, an Investigational Device Exemption (IDE) is required for this.

The second variant is data collection as part of a clinical study. The FDA points out that participants there are usually trained differently and supervised more closely than users in everyday life, and that the data must be read in this light. In addition, the samples are usually considerably larger so that the results are statistically robust. If the device is used at home, direct observation is often limited. The guidance then considers it insufficient to rely on self-reports alone and recommends supplementing them with observational data where possible.

Field observation in the development phase is to be distinguished from both variants. In a contextual interview (in the guidance: “contextual inquiry”), users are observed with an already marketed, similar device in the actual use environment. This serves understanding, not proof of the usability of the new device.

When which setting is common

Human factors validation testing is, according to the guidance, generally conducted under simulated use conditions. The guidance calls for tests under actual conditions when simulated use methods are not sufficient to assess how users interact with the device. This decision should be based on the preparatory analyses, that is, on the identification of the critical tasks and the use-related risks.

As examples, the guidance states that some aspects of a prosthetic leg or of a programming device for hearing aids cannot be simulated. The results of a test of a home dialysis machine in a conference room might also not transfer to use in an apartment. The test under actual conditions should be preceded by a suitable simulated use test so that the device is designed to be sufficiently safe for use, as far as a simulation can ensure that.

Knowledge tasks are a special case. Some critical tasks concern the understanding of information and cannot be assessed by observing behavior. As an example, the guidance mentions the warning never to use a device in an oxygen-rich environment. Such knowledge is tested by asking participants open, neutrally worded questions, without creating a real environment for it. For the summative evaluation as a whole, the following applies: The FDA points out that the term “summative testing” is sometimes defined differently and that some definitions omit essential components of validation.

Advantages and disadvantages compared

The following comparison is a professional assessment by the author. The statements on training, supervision, sample size, observability and IDE are supported by the guidance; the other points are based on experience.

On data protection and ethics, the guidance states for studies with participants that the responsible Institutional Review Board (IRB, the US ethics review body) should assess which safeguards for safety and privacy are needed, including informed consent forms. In the EU, Articles 62 ff. of the Medical Device Regulation (MDR) apply to clinical investigations conducted to demonstrate the conformity of a device. Whether a specific real use study falls under them must be clarified case by case.

Distinction from the online study

An online study is a setting of its own: Participants take part remotely, and the moderator usually sees the device or software only through a platform. The FDA human factors guidance does not address this setting. Because validation requires realistic conditions, the final user interface and observation of actual handling, a purely online study is hard to justify as validation for devices with physical operation. For early formative questions or for knowledge questions, however, it can be useful.

This is the author’s professional assessment, not a statement by the FDA. For pure software, the difference may be smaller. If manufacturers plan an online study in a validation context, they should agree on the approach with the agency in advance, for example through a Pre-Submission.

Human factors relevance

Four points from the human factors process are decisive for the choice of setting. First, the use environment: lighting, noise, distractions and space conditions can affect operation. The more strongly they determine the risk, the more precisely the simulation must reproduce them, or the more likely real use comes into consideration. Second, training: In both settings it must correspond to the actual training. Third, the participants: They represent the intended users, and where there are several distinguishable groups, each group. Fourth, the critical tasks: All of them are performed in the test or, for knowledge tasks, covered by questioning.

Observed use errors and close calls are recorded in both settings and discussed with the participants after the use scenarios. For use at home, this applies especially, because direct observation is often limited there.

Frequently asked questions (FAQ)

Sources

• FDA Guidance: Applying Human Factors and Usability Engineering to Medical Devices (Final Guidance, February 2016, revised August 2026)
• Regulation (EU) 2017/745 on medical devices (MDR)
• 21 CFR Part 812, Investigational Device Exemptions

Related terms

• Human factors validation testing
• Summative usability evaluation
• Formative usability evaluation
• Use environment factors
• Representative users
• Critical task
• FDA human factors guidance

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