Apdex score

Apdex is a numerical measure of user satisfaction with the performance of the applications. Refer our blog on "Measure end-user satisfaction with Apdex''. The index is based on three zones of application responsiveness:
• Satisfied: The user is fully productive. This represents the time value (T seconds) below which users are not impeded by application response time.
• Tolerating: The user notices performance lagging within responses greater than T but lesser than 4T, but continues the process.
• Frustrated: Performance with a response time greater than 4T seconds is unacceptable, and users may abandon the process.
Apdex Score is based on the universal Apdex formula,

Apdex = (Satisfied Count + Tolerating Count / 2) / Total Samples

The Apdex score is based on a uniform scale of 0 to 1.
• 0 = no users satisfied
• 1 = all users satisfied
For example, say 500 ms is configured as the Apdex Threshold,
•  If the response time is less than 500 ms, it will be counted as Satisfied
•  If the response time is less than (500*4) = 2000 ms, it will be counted as Tolerated
•  If the response time is greater than (500*4) = 2000 ms, it will be counted as Frustrated
This calculation is then followed by getting to know the number of visitors for the corresponding response time. For a 5 min poll interval, we get 288 data points per day. Say,
• If the response time is less than 500 ms for 40 times, then the satisfied count will be 40
• If the response time is less than 2000 for 200 times, then the tolerated count will be 200
• If the response time is greater than 2000 ms for 48 times, then the frustrated count will be 48
Thus,
Apdex = (Satisfied Count + Tolerating Count / 2) / Total Samples

=> (40 + (200/2))/288 = (40 + 100) / 288 = 140/288 = 0.486 = 0.47
Thus, this shows that its time to speed up your website and improve its usability. Refer here for some tips on Web Performance Optimization