Usability-Errors

Usability Error Definition (Draft 2006-10-01)

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What is a usability bug? (Short Version)

A Usability bug is an error that occurred while designing the user interface, so that

the User Interface is not

• effective, which means the user cannot do what he or she wants to do
• efficient, which means the user cannot do what he or she wants to do in a convenient or time saving way
• satisfactory, which means, the usage of the interface is annoying ...

Examples:

• The usage of an interface should be easy (or easy to learn)
• The elements should be self explaining
• The elements should be clearly visible/readable.
• Things should be there where the user expects them to be.

What is NOT a usability bug (in the stricter sense)

• Hardware problems such as my hardware xyz is not detected
• Hardware - Software conflicts such as software xyz crashes while trying to save on floppy disk

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What is a usability "bug" and what is not? (long version)

It is very difficult to create a definition of an usability error. One famous definition of usability is placed in the ISO 9241-11 document: "[Usability refers to] the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of user." (find more definitions here)

So if the user cannot achieve his goal with effectiveness, efficiency and some satisfaction, the software shows a problem concerning the usability. This is clear, but in the last consequence, a hardware driver bug preventing the system from booting could also be a usability bug because the user cannot achieve his goal and perhaps is very angry.

So we need a more practical approach to a usable usability error definition!

Perhaps we can make a difference between

• the system does not work properly based on an "error" in the code = not a usability bug
• and the user cannot work properly based on an "error" in the user interface design = usability bug where usability "errors" can be visible in
  • Macro-usability
    • Integration into other software
    • Dialog workflow
    • Content presentation
    • Etc.
  • and Micro-usability
    • Use of spatial coding principles to place dialog elements
    • Size or color of dialog elements
    • Correct use of shortcut-keys
    • Etc.

List with examples

Not a usability error

• When I enter my password into the login manager, the system will freezes after hit of the "Return"-key
• My Laptop does not make the save-to-disk procedure properly

Usability errors

• I cannot verify my username in the loginmanager, the height of the text entry field is to small and the font is cut

Usability Severity Codes

Source: http://www.stcsig.org/usability/resources/toolkit/toolkit.html

1 – Severe (Showstopper)

An emergency condition that causes the customer’s system to fail or causes customer data to be lost or destroyed. A showstopper usability bug can also be one that is likely to cause frequent data integrity errors. There is no workaround to these problems. A key feature needed by many customers is not in the system.

EXAMPLES:

• An obvious competitive feature is missing, or the customer expects something reasonable, but the feature isn’t there.
• Critical data is lost often because users are expected to “know�? to save their data or do something that is complex to preserve the data. For example, if the application allows users to exit without prompting them to save their changes or asking if they want to save a session.
• The usability problem is likely to result in an error that will cost the customer a large amount of wasted time or money (for example, a problem that would delay the recovery of a transaction database)
• The usability problem is likely to lead to a significant safety or health risk.
• Legal issues like missing copyright notices or improper use of another company’s trademarks

2 – High

A serious condition that impairs the operation, or continued operation, of one or more product functions and cannot be easily circumvented or avoided. The software does not prevent the user from making a serious mistake. The usability problem is frequent, persistent, and affects many users. There is a serious violation of standards.

EXAMPLES:

• There is no keyboard access method for a feature.
• The way to work around the problem is very hard to explain or hard to remember. The problem is likely to result in many support calls.
• Missing or undocumented parameters, menu commands, or other important information in the interface or documentation.
• Serious violations of corporate user interface design standards
• Offensive, inappropriate, or non-standard icons for standard functions
• Missing feedback for critical operations

3 – Medium

A non-critical, limited problem (no data lost or system failure). It does not hinder operation and can be temporarily cicumvented or avoided. The problem causes users moderate confusion or irritation.

EXAMPLES:

• Keyboard access is possible, but not easy. Tab order does not follow the user interface guidelines
• A common menu item or toolbar button does not do what is normally expected.
• Incorrect or no error messages (this could be High or even a showstopper in some cases if a bad error message results in lost data)
• Incorrect data are generated (this could be a high or a showstopper bug if it causes the user to make a bad decision that has significant implications for the user or company)
• Noticeable performance inefficiences (this can be a high if the performance is bad enough)
• Use of the wrong control in the interface (the wrong control causes some moderate performance degradation
• Missing or incorrect titles or units
• Unneeded clutter that does not have a major impact on user performance

4 – Low

Non-critical problems or general questions about the product. There are minor inconsistencies that cause hesitation or small aesthetic issues like labels and fields that are not aligned properly. EXAMPLES

• Typos (this could be a higher priority if they are in key places like menus or splash screens)
• A menu item does not use the recommended access character
• Small cosmetic problems