Hierarchical task analysis is a systematic method used by UX designers to evaluate the user steps of an existing system or, alternatively, how they might function when creating a new product. This valuable tool uncovers the multiple tasks required to achieve a specific goal.
Typically, it is used as a discussion platform for product assessment, development, and creation, but has various alternative valuable uses; for example, producing journey maps and prototypes, training and onboarding new staff to software and operational systems, or as a communication tool when examining user interaction.
It was originally used within Human Factors Engineering to evaluate and improve human performance but has been adapted to great effect as a UX design and research method. In hierarchical task analysis, we explore major tasks (carried out to achieve goals through relevant scenarios) known as operations in Human Factors Engineering.
The definition of hierarchical task analysis:
Hierarchical task analysis (HTA) is a structured approach to mapping the steps required for a user to achieve a specific goal. It delivers an easy-to-understand guide of how a system operates and can be used in various ways for differing applications.
Ultimately, hierarchical task analysis enables UX designers, researchers, and developers to understand what a system does and how it does it. It also delivers valuable insights into users’ needs and operations, uncovering pain points and alternative ways to complete specific tasks or utilise tools.
According to the Nielsen Norman Group, “Task analysis is the systematic study of how users complete tasks to achieve their goals. This knowledge ensures products and services are designed to efficiently and appropriately support those goals.”
Why use hierarchical task analysis?
- For analysing tasks within a hierarchical structure.
- To objectively compare different approaches to the same task.
- To measure task performance, providing a risk assessment of human error within users tasks.
- To capture multiple implementations of a reusable UX design pattern applicable for further interactions and operations.
Ultimately, we use hierarchical task analysis to understand and improve the user experience of products and systems. It allows us to directly observe user interaction, behaviours, thought processes, and feelings.
Displaying a product’s hierarchical structure is an excellent method for presenting complicated tasks and complex systems, providing a clear visual map of the many steps taken as users complete tasks.
With this deeper understanding, we use the information we gather to improve such systems and user interfaces or to create efficient new systems, journey maps, and more.
One of the key uses of hierarchical task analysis is to observe the different ways users complete tasks. There are often several ways to achieve the same goal or parent task. Describing user interactions to detail how they achieve goals provides options for streamlining and improving each structured approach.
What are the key elements of a hierarchical task analysis?
- User goal or primary task – The overall objective of the task, highlighting user needs or studying the tasks users must complete to achieve product and shareholder goals.
- Subtasks – Charts or lists that outline the task structure.
- The task hierarchy plan – Documents that outline the task sequence.
Each primary task—defined by its goal—is broken into a list of subtasks, with a separate plan that specifies the order in which they are carried out.
Task hierarchy
The primary tasks outline the basic steps required to complete the goal through a specific numbering scheme, with their subtasks broken into specific, separate steps. The detail and number of subtasks depend on the depth of analysis deemed necessary by the study operators.
- 1 User goal
- 1.1 Subtask
- 1.1.1 Subtask step
- 1.1.2 Subtask step
- 1.1.3 Subtask step (etc.)
- 1.2 Subtask
- 1.2.1 Subtask step
- 1.2.2 Subtask step
- 1.2.3 Subtask step (etc.)
- 1.3 Subtask
- 1.3.1 Subtask step
- 1.3.2 Subtask step
- 1.3.3 Subtask step (etc.)
- 1.4 Subtask (etc.)
- 1.4.1 Subtask step
- 1.4.2 Subtask step
- 1.4.3 Subtask step (etc.)
- 1.1 Subtask
The hierarchical task analysis plan
The plan is typically a separate document outlining the order of the subtask steps. For example, if we consider a goal of buying a product, subtasks would include locating an item, adding the item to the basket, entering the checkout system, entering the necessary customer, delivery, and payment details, and finally completing the purchase. However, as the customer enters the checkout system, they could have options to continue as a guest, register a new account, or log in using an existing account.
The plan would dictate the order of the subtasks depending on which option the user preferred. Additional options, for example, might include using PayPal, Apple Pay, or Google Pay to streamline the checkout system, using already completed delivery addresses and customer details. Perhaps another option would include a one-click express purchase option for already logged-in registered users. A plan considers all such multiple tasks and maps out the relevant route through their complex tasks.
The plan specifies the relevant subtasks and subtask steps for each alternative option, where the task hierarchy diagram includes all the stages and steps in a linear order. For example, the HTA diagram will include all the streamlined payment options in a list:
- 1 Enter the checkout system
- Carry out in order unless using PayPal, carry out steps 1.1.1; using Apple Pay, carry out steps 1.2.1; using Google Pay, (etc.) … ; moving to step 1.7 on completion of the relevant subtasks:
- 1.1 Click PayPal
- 1.1.1 (and more) PayPal subtasks
- 1.2 Click Apple Pay
- 1.2.1 (and more) Apple Pay subtasks
- 1.3 Click Google Pay
- 1.3.1 (and more) Google Pay subtasks
- 1.4 Continue as a guest
- 1.1.1 (and more) guest user subtasks
- 1.5 Register account
- 1.1.1 (and more) customer registration subtasks
- 1.6 Login to an existing account
- 1.1.1 (and more) existing user login subtasks
- 1.1 Click PayPal
The plan for our fictional checkout system specifies that the user must execute step 1.2 to use Apple Pay. Depending on the depth and detail of the task analysis, the Apple Pay option will have its own list of tasks beginning at 1.2.1, guiding the reader through that part of the system process.
Presenting your HTA analysis
There are various ways to present a hierarchical task analysis: using a standard flow chart, operation-sequence diagrams, detailed lists, illustrations, screengrabs, or, ideally, combinations of each are ideal to produce a comprehensive graphical representation of the task steps.
Each task analysis will include the reason and goals behind the exploration, the observational methods, and the information gathered about each task performance. All this information will be compiled into an easily digestible set of diagrams, lists, and plans. A consistent approach is required from team members to ensure an easy-to-understand direct comparison between use case approaches.
Hierarchical task analysis UX tools
We can utilise various standard UX research tools as task analysis methods. Experienced practitioners will be able to match the ideal option to the needs of each study.
- Contextual inquiry allows researchers to monitor users performing tasks in their usual environment.
- Critical incident technique interviews provide information about how and when users faced specific issues and tasks while using the product.
- Usability testing – Users are observed as they complete tasks.
- Diary studies and record keeping can help uncover the regular tasks users carry out and their associated issues.
- Activity sampling allows researchers to monitor and record users over time to discover product and task operation duration and frequency.
- Simulations allow researchers to walk through the task steps users typically take.
Observation is a crucial part of hierarchical task analysis research. Interviews and surveys aren’t as efficient in uncovering many of the valuable insights designers need to consider to enhance product UX.
How do you conduct a hierarchical task analysis?
Typical steps for a hierarchical task analysis include:
1. Preparation and research
Your preparation should include the consideration of user needs, users tasks, pain points, target users, and how the system functions in its typical use.
2. Define the reason behind your task analysis
Why do you need to map out the system structure? This will guide the areas you must explore and the required task steps.
3. Build an initial flow chart
Given the complex tasks and systems of digital products, building a complete hierarchical task analysis becomes an iterative process. Initially, you should focus on each task step required to complete the given task, considering the interactions between different system components.
4. Develop each sub-task and smaller sub-tasks
As you collect data, add further detail to develop the diagram and deliver a clear understanding of the complete tree structure.
5. Iterate: review and repeat
Review the finished version with stakeholders and users to check for missing steps or sub-goals, ensuring the finished version is a complete study. If further steps are required, consider which other methods you can use to uncover the relevant data.
6. Deliver the report and your recommendations
Your report is merely a single step in the design process. Each HTA is a tool to help understand the system and how users manage simple and complex tasks. Your report reviews its performance and suggests ways and areas of improvement to enhance operation, user interactions, and, ultimately, its success in the marketplace.
Summary
Hierarchical task analysis is an incredibly useful tool for examining digital products with complex systems to explore and develop the goals and tasks users interact with. It’s a relatively straightforward and standard practice amongst UX designers and researchers and delivers valuable insights for procedure development, journey mapping, and defining its ideal user personas.
Used hand-in-hand with other standard UX observational methods, we can deliver a graphical representation of the map we need to navigate and upgrade performance and user experience.
If you would like to know more about hierarchical task analysis email us at hello@ux247.com.
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