Thesis - Instituto de Telecomunicações

126 CHAPTER 6. APPLICATIONS AND RESULTSFigure 6.8: Confusion matrix for an 1 sample EDA classifier.Uncertainty Based Reject OptionThe uncertainty based reject option (see section 5.4.2) was tested with the EDA data tounderstand the possible use of the EDA signal as a stand-alone mode, even if a relevantpercentage of the samples would need to be rejected.The identification error probability - probability of rejection trade-off is depicted in figure6.10 for the standard rejection option classifier (solid line) and the proposed uncertaintybased reject option classifier (dashed line). The example is from a sequential classifier with5 sequential samples (the training vector had 5 sequential samples per user). The bootstrapestimates were computed from 100 bootstrap samples.We see that the uncertainty based rejection classifier presents lower error probability forthe same rejection level. If we select a fixed error probability, the uncertainty based rejectoption also has lower rejection levels when compared to the standard reject option.