I am trying to understand how a Trigger efficiency plot should be interpreted in the scenario of an analysis that is using that trigger. What does a turn-on curve tell us about events that pass the trigger? One example (I think it's PUBLIC so it's accessible): https://twiki.cern.ch/twiki/bin/view/AtlasPublic/MissingEtTriggerPublicResults or in particular a plot like this: https://twiki.cern.ch/twiki/pub/AtlasPublic/MissingEtTriggerPublicResults/Preliminary3_Wmunu_L1.png In the plot one can see that the HLT_xe70 (that works together with the L1_xe50) efficiency is not that well where it's supposed to be (@70GeV). That means that a lot of events that don't pass the trigger requirements, actually do... is that the right way to read it? But also what is that curve telling me of an event with Etmiss of let's say 90GeV and an event of 30GeV that actually fire the trigger?