How is the Apdex score calculated?

How is the Apdex score calculated?

The Apdex score is determined based on the following criteria:

If the total response is less than the provided threshold, the score is set to 1.
If the total response is less than four times the specified threshold, the score is set to 0.5.
If the total response exceeds the specified threshold, the score is set to 0.