If you could only ask one question, use this one.

Jeff Sauro • March 2, 2010

Was a task difficult or easy to complete? Performance metrics are important to collect when improving usability but perception matters just as much. Asking a user to respond to a questionnaire immediately after attempting a task provides a simple and reliable way of measuring task-performance satisfaction. Questionnaires administered at the end of a test such as SUS, measure perception satisfaction.

There are numerous questionnaires to gather post-task responses, some of the more popular ones are :

1. ASQ ^PDF: After Scenario Questionnaire (3 Questions) 
2. NASA-TLX : NASA's task load index is a measure of mental effort (5 Questions) 
3. SMEQ^PDF: Subjective Mental Effort Questionnaire (1- Question)
4. UME^PDF : Usability Magnitude Estimation  (1-Question)
5. SEQ ^PDF: Single Ease Question

The SEQ is a new addition which Joe Dumas and I tested two years ago ^PDF and found it to perform very well.  In addition to the usual psychometric properties of being reliable, sensitive and valid, a good questionnaire should also be:

1. short
2. easy to respond to
3. easy to administer
4. easy to score

The SEQ is all four. You can administer it on paper, electronically on any web survey service or even verbally.

Overall, this task was?

Very Difficult						Very Easy

Figure 1: The Single Ease Question (SEQ).


For the past year I've been collecting data using the SEQ on numerous tasks on websites and applications. My goal is to assemble a large database of tasks to generate a standardized post-task SEQ score. It would be nice to have standardized task completion rates and task times for classes of tasks but I've found slight differences in tasks scenarios make aggregating data difficult.

The beauty of the SEQ is that users build their expectations into their response. So while adding or removing a step from a task scenario would affect times, users adjust their expectations based on the number of steps and respond to the task difficulty accordingly. On your next task use the SEQ.

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Posted Comments

There are 5 Comments

November 1, 2011 | sahil wrote:

Why railways having sleeper on ralway track.........................................................................................?rn 

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April 7, 2010 | Timo Jokela wrote:

David: a bit delayed comment. My setting is creating usability requirements into a RFP. I would like to set a verifiable usability requirements as acceptance criteria for the system to be developed. 

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March 18, 2010 | David Bishop wrote:

Timo, Jeff, we've found that in many cases, it's more important to show that usability is improving than to have a specific numerical requirement for 'good.' Pessimists could chalk this up to state of the art (usability is generally poor enough that any raising of the bar will be of value). Optimists can point out that an organization that measuring usability and aiming for improvement is an organization that has a mature process (à la CMM), which may be more important that setting a specific target. 

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March 13, 2010 | Jeff Sauro wrote:

Timo, Great question. Rating scale data is only as good as what you can compare the results to. With the SEQ I have used it for over 100 tasks so my raw scores can be expressed as a percentile rank. Later this year I'll talk more about that database so others can generate standardized ease scores by task. 

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March 11, 2010 | Timo Jokela wrote:

I would be most interested to use a question such as SEQ for usability requirements.

But what would be the value for 'good' usability? Is 7 good enough? Or 8?

How would you comment on this? 

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