Who Needs a Task Analysis Anyway?

Who Needs a Task Analysis Anyway?

This is an excerpt from the Applied Human Factors in Medical Device Design book see link on the side for purchase

Task Analysis Overview

A task analysis is the process intended to identify a user’s goal, what steps must be done in order to achieve the goal, what experiences (personal, social and cultural) users bring to the tasks and how the environment might influence the user. It is an important design tool that can be effectively used early in the design process (i.e., before the creation of device prototypes) to help inform use-related design of the user interface (UI) components. Throughout the design process, a task analysis can also be used as a fundamental framework to the development of use-related risk documentation (e.g., uFMEA or Fault Tree Analysis), human factors protocol development, and usability evaluation. It can highlight elements of the user-device interactions that could be problematic for users, which provides designers opportunities early and throughout the product development process to implement risk mitigations proactively, ultimately saving time and manufacturing costs.

Overall Process - Figure 1 illustrates the task analysis process starting from identifying use cases (Step 1 in the process) and in some cases (uFMEA) ending with determining potential harms and severity of harm (Step 6 in the process).

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Figure 1. Process map of an example task analysis development process.

The terminology used in a task analysis may vary across device teams. The terminology used in this chapter includes terms such as; “use cases,” tasks,” and “sub-tasks.” Although terminology may change slightly or have somewhat different meanings across manufacturers, it is important for a manufacturer to use a systematic and consistent hierarchy when creating and utilizing a task analysis and associated terminology.

Step One: Use Case Identification

The first step in developing a task analysis is use case identification. Use cases are an important input to the task analysis as they provide context for the various, sometimes overlooked, uses of a device. Most medical devices involve numerous use cases. While some use cases are related to the main purpose of the device such as drug delivery or running a diagnostic test, other commonly overlooked use cases for some devices that should be considered in the task analysis if they are applicable include procedures such as maintenance, calibration, reprocessing, cleaning, disposal, shut down, and storage. Different users of the device may encounter the same or different use cases.

Step Two: Task Identification

Upon definition of the use cases, the tasks associated with each specific use case can be established. Tasks may be determined from knowledge experts (e.g. clinical stakeholders) input, FDA feedback on similar devices, observations of users with similar devices, human factors experts interacting with the device, critical thinking, investigation into videos of device use or similar device use, instructional material, risk documentation, reverse engineering and/or experience with similar devices. When identifying tasks, it is important to analyze the user performance requirements, referencing that the device must support the user(s) towards meeting their intended goal. This analysis may include a heuristic review or cognitive walk through of the design for various use cases with the intended user in mind.

Step Three: Sub-task Breakdown

During the sub-task breakdown stage, each task should be broken down into independent actions or processes. Most often it is important to avoid combining multiple tasks into a single line item of the task analysis, as this introduces the possibility of misidentification or omission of associated use requirements and potential use errors as well as “double counting” errors and losing specificity in data reporting during usability testing. When task analyses are used during the design process as the framework for human factors testing, appropriately separated tasks and sub-tasks are also important because they guide moderator observations and the debriefing interview so as to yield insights into root cause analysis and reporting of any observed difficulties and use errors.

Additionally, when breaking down tasks into sub-tasks, it is important to integrate order and timing (when applicable) in an observable and quantifiable way. Verbiage should be concise, consistent (with no ambiguity) and measurable (which becomes extremely important when task analysis guides usability testing). For example, terms such as “after” and “before” should be included when order is important. When timing is critical, measurable metrics should be included. For example, instead of “hold until the medication has been delivered,” provide a metric such as “hold for 5 seconds until the medication is no longer visible in the window.”

The precision of wording included in task analysis can influence the quality of the analysis. It is important to avoid using words that are ambiguous and will be difficult to observe or measure (e.g., “adequate,” “well,” or “enough”). Instead define what is meant by ambiguous words with as much detail as possible that describes the specific UI components and the expected user-device interactions. The more specific and stand-alone the sub-tasks can be, the more useful a task analysis will be as an early design tool as well as a framework for subsequent human factors data collection and analysis.

Step Four: Apply the Perception, Cognition, and manual Action (PCA) Model

A complete task analysis is fundamental to user interface optimization, use error prediction and prevention, and determination of the user’s interactions with the device relative to task requirements. These user task requirements include user actions, user perception of information and user cognitive processes[1]. A Perception, Cognition, and Manual Action (PCA) model is an FDA recommended strategy for task analysis that is used to identify user-device interactions and characterize user capabilities. Applying PCA to a task analysis adds specific user requirements that lend support for identification of potential use errors and root cause analysis during human factors testing. This model identifies user actions related to the perceptual inputs, cognitive processing, and physical actions involved in the task[2].

Step Five: Potential Use Error Identification

The next step is to identify possible use errors and impacts of not meeting the use requirements. Use errors and difficulties observed during tasks can be traced back to the PCA requirements for each task, which can assist in determining the root causes for issues and the corresponding piece of the device user interface that may require redesign or additional risk mitigation evaluation. Potential use errors may occur if the user is unable to understand or carry out the user interface requirements.

Another part of use error identification includes leveraging data from prior formative evaluations, literature (e.g., peer published articles, FDA news flashes, device recalls), customer complaints, post-market data from similar devices and expert opinions of stakeholders (including clinical experts) on the potential use errors and the consequences of those use errors. If a user does not understand the tasks or is not able to complete the tasks, the device may be used incorrectly or may not be used at all. This could lead to decreased treatment efficacy or delay in therapy or treatment. Having input from multiple stakeholders with regard to use errors and associated consequences is critical to understanding all of the risks associated with the device use.

Step Six: Potential Harm Identification

Using task analysis as the foundation of risk analysis is a best practice. ANSI/AAMI HE75[3] defines harm as “(1) Physical injury or damage to the health of people, (2) damage to property or the environment.” A risk is defined as a, “Combination of the probability of occurrence of the harm and the severity of the harm”[4]. The probability of occurrence is the frequency with which the harm would occur. Severity is the measure of the possible consequences of a hazard. Although harm, probability of occurrence, and severity should all be considered in determining the risk profile for a particular device, probability of occurrence is not an FDA-accepted factor for determining the criticality and corresponding categorization of tasks in human factors testing. The estimated probability of occurrence of a problem is not always accurate, and many use errors are not anticipated until device use is simulated and user interaction with the device is observed, or even later once the product is released and the manufacturer observes post-market problems. Therefore, severity and potential harm are preferred measures for determining if user interface modifications are required to reduce or eliminate harm[5] and should therefore be included in a task analysis.

Using Task Analysis for Instructional Design

A task analysis is a critical input for instructional designers while creating the device’s instructional materials (e.g. Instructions for Use (IFU), quick reference guide (QRG), user manual or training materials). Instructional designers rely on the task analysis as an outline for the necessary steps, formatting and structure of the instructional material. The goal of the instructional material is to guide accurate, safe and effective user performance with a device, which is defined by the task analysis. It is important to note that relying solely on the IFU and risk documentation to develop a task analysis will not produce a comprehensive task analysis and may inaccurately identify use errors.

Task Analysis as a Design Tool

A task analysis serves as a tool throughout the design process. In addition to providing the foundation for task identification and task categorization, a task analysis can play a crucial role in improving device design. Device designers can utilize the task analysis and corresponding Perception, Cognition, and manual Action (PCA) Model to prioritize design features associated with critical tasks and implement mitigations to prevent use errors from occurring. Additionally, task analysis can lead to a more efficient and effective design related to human performance, including safety and productivity.

When developed and used correctly, a task analysis is an invaluable tool for improving device design, serves as a fundamental input to instructional material development, provides insights into use-related risks and user-device interactions that could be problematic for users.


[1] Sharit, J. (2006). Handbook of human factors and ergonomics. Handbook of Human Factors and Ergonomics. https://doi.org/10.1002/0470048204.ch27

[2] U.S. Department of Health and Human Services Food and Drug Administration Center for Devices and Radiological Health. (2016). Applying Human Factors and Usability Engineering to Medical Devices.

[3] ANSI/AAMI HE75. (2009). Human factors engineering - Design of medical devices.

[4] ANSI/AAMI 14971. (2010). Medical devices— Application of risk management to medical devices American National Standard.

[5] ANSI/AAMI 14971. (2010). Medical devices— Application of risk management to medical devices American National Standard.

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