Averages are lossy and do not accurately represent the spectrum of experience. The idea behind the Apdex score is to produce a single metric between 0 and 1.0 to represent the range of performance.
First a “Apdex target response time” should be configured for a given check, in this example we’d like the website to respond in under a 1000ms. If you’re unsure simply leave the default.
Configured with a target of 1000ms we get an Apdex score of 0.71 which means we’re not quite hitting our target, as it should be 1.0. This indicates that a portion of visitors or customers may not be satisfied with the response time.
If we edit the check and change the “Apdex target response time” to 500ms, you’ll see that now the chart displays that we’re not reaching our target roughly half the time, also indicated by the low Apdex score of 0.59.
The Geography section of each check also utilizes Apdex to color regions indicating response time and errors.
In short you should set the target latency to what you find is an acceptable duration, and try to score 1.0.
Apdex is calculated using the following formula:
apdex = (satisfied + (tolerated / 2)) / samples
Apex Ping treats errors as frustrating, and they are reflected in the Apdex score, thus this score becomes a reflection of latencies and errors. You can find more information regarding Apdex on the Wikipedia page.