This Apdex Calculator teaches people how Apdex works by letting them practice calculating the Apdex score of some randomly-generated metrics, and see how changing the Apdex threshold affects the score.
See it in action here: https://newrelicuniversity.github.io/apdex-calculator/
Each time the Apdex Calculator loads, it generates 10 random response time values between 100 and 8000; the apdex_t defaults to 1000. Given these metric and threshold values, the user is prompted to calculate the resulting Apdex score. They may enter their answer in the field labeled My Apdex and click the Am I Right? button to check their work.
The Give me a hint link provides a reminder of how Apdex is calculated, including a breakdown of how the provided metric values fall into the Satisfied, Tolerating, and Frustrated categories.
It is also enlightening to change the apdex_t value and see how it changes the distribution of metrics among Satisfied, Tolerating, and Frustrated. In other words, given this set of metrics, what should the Apdex threshold be in order to get an Apdex score between 0.85 and 0.95?