Most research on quality of life uses observed scores obtained from surveys and questionnaires to make conclusions and inferences regarding quality-of-life outcomes. False responses on patient questionnaires can be caused by aberrant answers, guessing, inattentiveness (which may result from fatigue), misunderstanding or response misfit, according to item response theory [9,10].
These issues can result in false alarms (i.e., false positive and false negative errors) coming from medical diagnoses and leading to make vain efforts in actions taking. It is of
interest to discuss the possibility of replacing observed response scores with expected ones to make decisionsand inferences by applying probability theory to studiesof quality-of-life outcomes.