This thesis presents two diboson measurements with the ATLAS experiment. The first is a differential measurement of Higgs boson observables in the four-lepton decay channel at $\sqrt{s}=8$ TeV. The second presents a first measurement of the WZ diboson production cross section in the three-lepton decay channel at $\sqrt{s}=13$ TeV. Special emphasis is given to the identification techniques of prompt electrons, particularly the likelihood identification first introduced in 2012 data taking, and electron efficiency measurements in the ATLAS detector.