Apdex Score

Apdex (Application Performance Index) is an open standard to measure the user satisfaction regarding a web application. It is a metric that provides a single score ranging between 0-1 (0 = no users satisfied, 1 = all users satisfied), giving business application owners an insight into the measure of their customer happiness and satisfaction levels.

Easy to calculate and interpret, the data collected over a period of time are converted into a simple index based on the application responsiveness. Application responsiveness is categorized into three zone based on the Apdex score:

The value T can be defined by the application owners

The Apdex Score is calculated using the following formula:

              Satisfied Count + Tolerating Count

 Apdex =                                              2                

            Total Samples

  • Satisfied: This represents the time value (T seconds) below which users are not impeded by application response time. Depicts the user is fully productive.
  • Tolerating: This represents response time greater than T (precisely, T to 4T), where the user notices performance lagging but continues the process, which depicts the response is tolerated by the user.
  • Frustrated: This represents response time F, greater than 4T which is unacceptable, and users may abandon the process, which depicts the user is frustrated.

The score of 1 show all the users are satisfied with the application performance, whereas a score of 0 show no users are satisfied. Score of 0.5 shows all the users are tolerating the application performance. As the application responsiveness vary, the score ranges from 0-1.

Apdex Score, as a whole, is critical to measure the service levels and customer satisfaction which in turn measures the business growth. Moreover, these values are easy to decipher; unlike the traditional values of average response time and throughput, that does not accurately interpret a particular transaction that is performing slow and affect user satisfaction.