IntroductionThe nature of evidenceProbabilityClinical endpoints of benefits and harmsStatistical expressions of benefit and harmBias and confoundingSystematic reviewsRandomized controlled trialsGeneral principlesStopping rulesAnalysis of subgroupsSafetyGeneralizabilityObservational studiesGeneral overviewHistorical controlled trialsConcurrent cohort studiesCase-control designsDatabasesCase reportsQualitative researchApproaches and methodsUses in the evaluation of therapeutic interventionsEconomic evaluationGeneral principlesCost-effectiveness, cost-utility and cost-minimization analysesCost-consequences analysisDecision-makingFor individualsFor populations