I've always used the "difference between appdex and user experience index" (
https://answers.dynatrace.com/spaces/148/uem-open-q-a_2/questions/108663/difference-between-apdex-an...) as my reference/guide to explain UEI vs Apdex. I've always stated that apdex is response time Only and does not take into account errors. However, I've just recently come to realize that several of our actions that are showing as "frustrated" User Actions are actually responding in less than our response time threshold. The difference is they are unfortunately returning a 404 (not really because the page isn't there). The rules in the Error definition show for all 4xx to "mark the transaction as failed" and I believe this is immediately making it in the "frustrated" category. Is that right? Is this new behavior (I realize that post I had been referencing is a few yrs old) or have I just been explaining apdex incorrectly for the last several years. 😞 Does apdex take into account errors?