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.
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.
The Apdex Score is calculated using the following universal formula:
Satisfied Count + Tolerating Count
Apdex = 2
Total Samples
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 zones based on the Apdex score:
where, the value T can be defined by the application owners.
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 to 1.
Let us say 500 ms is configured as the Apdex threshold. In this case,
This calculation is then followed by getting to know the number of visitors for the corresponding response time. For a 5 minute poll interval, we get 288 data points per day. Say,
Thus,
Apdex = (Satisfied Count + (Tolerating Count / 2)) / Total Samples
= (40 + (200/2))/288 = (40 + 100) / 288 = 140/288 = 0.486 ~ 0.49
Therefore, the Apdex value obtained shows that it is time to speed up your website and improve its usability.