Response Time

Definition

The performance quality subfactor, response time, is the time that a business enterprise, application or component takes to initially respond to a client request.

• For a service.
• To be allowed access to a resource.

Measurement

Response time is typically measured in terms of:

• Actual time (e.g., milliseconds)
• Average time

Requirements

See response time requirements.

Mechanisms

Typical mechanisms for improving response time include:

• Displaying a constantly changing percent complete status bar, a hourglass, and a change in button appearance when the complete transaction results in a long latency period (e.g., an interaction involving large amounts of processing and database access over a low bandwidth network).
  For example, the application might display an hourglass on the user’s screen while waiting for a complex data query to return, be properly formatted, and displayed.

Guidelines

The following guidelines have been found to be useful when producing response time requirements:

• Response time can address the time taken to respond to client applications as well as human actors.
• Response time requirements are based on human psychological limits:
  • The average typist can type continuously if movements between fields are less than 0.2 seconds.
  • The average typist takes approximately 1.35 seconds to mentally switch gears when moving from one set of typing to another (which usually occurs when data entry clerks move from one screen to the next).
  • The average person will wait for no more than 20 seconds before looking for something else to do (and less if we are talking about an Internet shopper).