The 7 Steps of Hierarchical Task Analysis: Part 4

This is the fourth in our series of blog posts to teach you the basics of Hierarchical Task Analysis.  In our third post in this series, we explained exactly how to collect information for your analysis. In this post we are going to focus on how to verify the information your collected. 


  • Cross check with multiple information sources.  Don't expect to collect all of the information about the activity in one interview and get it right the first time.  Cross-checking your results with the original interviewee and other people who carry out the same activity will help you verify what you have collected and fill in any gaps.  Since reviewing written notes or tape-recorded interviews can be time consuming and error-prone, you may find it easiest to produce a summary of your findings and have them reviewed by subject matter experts.
  • Don't expect people to always follow the procedureThere are many reasons why someone might not follow the task structure as your references intend.  Maybe the user doesn't have time to follow the procedure so they have found a shortcut.  Perhaps they are missing a required tool, and they are improvising.  Understanding why there is a gap between how you think the task should be performed and how it is actually performed is a great opportunity for learning.
  • Review your results with your subject matter experts.  Ask probing questions to understand if there is variation in how a task is performed.  Dig to understand why and how this new understanding relates to your overall goal.             


Let's review our example's context.  You are a human factors engineer in a company that makes cars, and you are assigned to a team that is designing a website to help users with any questions they may have about their cars. You have already established the following in Step 1:

  • Goal:  Reduce demand placed upon customer support by providing a web based resource to answer frequently asked questions.
  • Stopping Rule:  Stop breaking down tasks when the task can be completed by the most unfamiliar of customers.
  • Properties: Expected time to complete, tools required, difficulty level of overall task, difficulty of individual task, importance, frequency, training content.


We have collected information from a web post, The 10 Most Important Things in Your Car Owner's Manual.  Obviously there is a lot more data that we would want to look at, but this is just a simple example.  We have created the following list of tasks as our candidates

  • How to Set Up Your Car
  • How to Check Your Fluids
  • How to Drive Your Car Better
  • How to Troubleshoot Common Problems
  • What is your Car's Frequently Used Technical Data
  • How to Achieve Ideal Tire Pressure
  • How to Keep Your Car Looking It's Best
  • What Does this "Fill in the Blank" Do
  • What Does My Warranty Cover

We have further broken down our procedure in one task to show finer detail....

  • How to Set Up Your Car
    • How to Set Your Clock (Do all steps in order)
      1. Turn the vehicle on
      2. Push and hold the display button
      3. Observe the dashboard display window change to the "Setting" display
      4. Observe whether option "Clock," "Display," or "Return" is highlighted
        1. If "Clock," is highlighted, push and hold Display until display changes again.
        2. If "Display" or "Return" is highighted
      5. etc...


Look for examples of how people might actually carry out this task. YouTube can often be a great source of information on this.

Even more enlightening are the comments on the YouTube site from actual car owners commenting on this procedure.  By reviewing the comments, we can learn the following:

  • Videos are found to be very useful, maybe we should use videos on our website
  • There is a suggestion to provide CDs with videos to car owners
  • There is a comment that the user manual may be incomplete - "not mentioning the DISP button"
  • There is a comment saying that there is more than one DISP on the car's interior which causes confusion

Even this short example of a simple procedure provides an opportunity to learn from the actual use of products.


You are now well on your way to performing your first Hierarchical Task Analysis.  You are ready to move on to the next step in Hierarchical Task Analysis, applying task analysis notation to your analysis.