Apdex - Application Performance Index

Apdex is an open standard developed by an alliance of companies for measuring performance of software applications in computing.

It is purpose is to convert measurements into insights about user satisfaction, by specifying a uniform way to analyze and report on the degree to which measured performance meets user expectations.

It is based on counts of "satisfied", "tolerating", and "frustrated" users, given a maximum satisfactory response time t, a maximum tolerable response time 4t, and where users are assumed to be frustrated above 4t. The score is equivalent to a weighted average of these user counts with weights 1, 0.5, and 0, respectively.

When engaging in application performance management, for example in the course of Website monitoring, enterprises collect many measurements of the performance of information technology (IT) applications. However, this measurement data may not provide a clear and simple picture of how well those applications are performing from a business point of view, a characteristic desired in metrics that are used as key performance indicators. Reporting several different kinds of data can cause confusion. Reducing measurement data to a single well understood metric is a convenient way to track and report on Quality of experience.

Measurements of application response times, in particular, may be difficult to evaluate because:

   Viewed alone, they do not reveal whether people using the application consider its behavior to be highly responsive for their particular needs, merely tolerable, or frustratingly slow.

   Using averages to summarize many measurement samples washes out important details in the measurement distribution, and may obscure evidence that many users may have been frustrated with application response times that were significantly slower than the average value.

   The objectives (or goals or targets) set for response time values are not uniform across different applications. This makes it difficult to view comparable data for several applications side-by-side (such as in a digital dashboard), and see quickly which are meeting their objectives and which are not.

The Apdex method seeks to address these problems.