Apdex
Encyclopedia
Apdex is an open standard
developed by an alliance of companies. It defines a standard method for reporting and comparing the performance of software applications in computing
. Its 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
.
, for example in the course of Website monitoring
, enterprises collect many measurements of the performance of information technology
(IT) applications. However, this measurement data rarely provides 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
. Reducing measurement data to a single well understood metric is the ideal way to track and report on Quality of experience
. Reporting several different kinds of data often confuses the picture, rather than clarifying it.
Measurements of application response time
s, in particular, can be obtained from many different measurement tools, yet once gathered, they are difficult to evaluate because:
The Apdex method seeks to address these problems.
The Apdex formula is the number of satisfied samples plus half of the tolerating samples plus none of the frustrated samples, divided by all the samples:
Apdext = (Satisfied Count + Tolerated Count / 2) / Total Samples
So it is easy to see how this ratio is always directly related to users' perceptions of satisfactory application responsiveness. To understand the full meaning of the ratio, it is always presented as a decimal value with a sub-script representing the target time T. For example, if there are 100 samples with a target time of 3 seconds, where 60 are below 3 seconds, 30 are between 3 and 12 seconds, and the remaining 10 are above 12 seconds, the Apdex is:
(60 + 30 / 2 )/ 100 = 0.75
, was founded in 2004 by Peter Sevcik, President of NetForecast, Inc. The Alliance is a group of companies that are collaborating to establish the Apdex standard. These companies have perceived the need for a simple and uniform way to report on application performance, are adopting the Apdex method in their internal operations or software products, and are participating in the work of refining and extending the definition of the Apdex specifications. Alliance contributing members who incorporate the standard into their products may use the Apdex name or logo where the Alliance has certified them as compliant.
In January 2007, the Alliance comprised 11 contributing member companies, and over 200 individual members. While the number of contributing companies has remained relatively stable, individual membership grew to over 800 by December 2008, and reached 2000 in 2010. To support the professional interests of the membership, in 2008 the Alliance began publishing a blog, the Apdex Exchange, and in 2010, instituted a program of educational Webinars. These activities address performance management topics, with an emphasis on how to apply the Apdex methodology.
Open standard
An open standard is a standard that is publicly available and has various rights to use associated with it, and may also have various properties of how it was designed . There is no single definition and interpretations vary with usage....
developed by an alliance of companies. It defines a standard method for reporting and comparing the performance of software applications in computing
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
. Its 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
User expectations
User expectations refers to the consistency that users expect from products. Interaction design is very concerned with this topic. For example, our user expectations for traffic behavior is one of the more consistent ones because it is governed by traffic laws that are enforced...
.
Problem addressed
When engaging in Application Performance ManagementApplication Performance Management
Application performance management, or APM, refers to the discipline within systems management that focuses on monitoring and managing the performance and service availability of software applications....
, for example in the course of Website monitoring
Website monitoring
Website monitoring is the process of testing and verifying that end-users can interact with a website or web application. Website monitoring is often used by businesses to ensure that their sites are live and responding....
, enterprises collect many measurements of the performance of information technology
Information technology
Information technology is the acquisition, processing, storage and dissemination of vocal, pictorial, textual and numerical information by a microelectronics-based combination of computing and telecommunications...
(IT) applications. However, this measurement data rarely provides a clear and simple picture of how well those applications are performing from a business point of view, a characteristic desired in metrics
Metric (mathematics)
In mathematics, a metric or distance function is a function which defines a distance between elements of a set. A set with a metric is called a metric space. A metric induces a topology on a set but not all topologies can be generated by a metric...
that are used as key performance indicators
Key performance indicators
A performance indicator or key performance indicator is an industry jargon for a type of performance measurement.. KPIs are commonly used by an organization to evaluate its success or the success of a particular activity in which it is engaged...
. Reducing measurement data to a single well understood metric is the ideal way to track and report on Quality of experience
Quality of experience
Quality of experience , some times also known as quality of user experience, is a subjective measure of a customer's experiences with a service...
. Reporting several different kinds of data often confuses the picture, rather than clarifying it.
Measurements of application response time
Response time
In technology, response time is the time a system or functional unit takes to react to a given input.- Data processing :In data processing, the response time perceived by the end user is the interval between the instant at which an operator at a terminal enters a request for a response from a...
s, in particular, can be obtained from many different measurement tools, yet once gathered, they are 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 averageAverageIn mathematics, an average, or central tendency of a data set is a measure of the "middle" value of the data set. Average is one form of central tendency. Not all central tendencies should be considered definitions of average....
s to summarize many measurement samplesSample (statistics)In statistics, a sample is a subset of a population. Typically, the population is very large, making a census or a complete enumeration of all the values in the population impractical or impossible. The sample represents a subset of manageable size...
washes out important details in the measurement distributionFrequency distributionIn statistics, a frequency distribution is an arrangement of the values that one or more variables take in a sample. Each entry in the table contains the frequency or count of the occurrences of values within a particular group or interval, and in this way, the table summarizes the distribution of...
, and may obscure evidence that many users may have been frustrated with application response times that were a significantly slower than the average value. - The objectivesService level objectivesA Service level objective is a key element of a service level agreement between a service provider and a customer. SLOs are agreed as a means of measuring the performance of the Service Provider and are outlined as a way of avoiding disputes between the two parties based on...
(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.
Apdex method
Proponents of the Apdex standard believe that it offers a better way to measure what matters. The Apdex method converts many measurements into one number on a uniform scale of 0-to-1 (0 = no users satisfied, 1 = all users satisfied). The resulting Apdex score is a numerical measure of user satisfaction with the performance of enterprise applications. This metric can be used to report on any source of end-user performance measurements for which a performance objective has been defined.The Apdex formula is the number of satisfied samples plus half of the tolerating samples plus none of the frustrated samples, divided by all the samples:
Apdext = (Satisfied Count + Tolerated Count / 2) / Total Samples
So it is easy to see how this ratio is always directly related to users' perceptions of satisfactory application responsiveness. To understand the full meaning of the ratio, it is always presented as a decimal value with a sub-script representing the target time T. For example, if there are 100 samples with a target time of 3 seconds, where 60 are below 3 seconds, 30 are between 3 and 12 seconds, and the remaining 10 are above 12 seconds, the Apdex is:
(60 + 30 / 2 )/ 100 = 0.75
Apdex Alliance
The Apdex Alliance, headquartered in Charlottesville, VirginiaCharlottesville, Virginia
Charlottesville is an independent city geographically surrounded by but separate from Albemarle County in the Commonwealth of Virginia, United States, and named after Charlotte of Mecklenburg-Strelitz, the queen consort of King George III of the United Kingdom.The official population estimate for...
, was founded in 2004 by Peter Sevcik, President of NetForecast, Inc. The Alliance is a group of companies that are collaborating to establish the Apdex standard. These companies have perceived the need for a simple and uniform way to report on application performance, are adopting the Apdex method in their internal operations or software products, and are participating in the work of refining and extending the definition of the Apdex specifications. Alliance contributing members who incorporate the standard into their products may use the Apdex name or logo where the Alliance has certified them as compliant.
In January 2007, the Alliance comprised 11 contributing member companies, and over 200 individual members. While the number of contributing companies has remained relatively stable, individual membership grew to over 800 by December 2008, and reached 2000 in 2010. To support the professional interests of the membership, in 2008 the Alliance began publishing a blog, the Apdex Exchange, and in 2010, instituted a program of educational Webinars. These activities address performance management topics, with an emphasis on how to apply the Apdex methodology.
External links
- Apdex website
- Apdex specifications
- Defining The Application Performance Index by Peter Sevcik, Business Communications Review, March 2005.