Introduction: in out-of-hospital cardiac arrest, early and efficient intervention through cardiopulmonary resuscitation (CPR) maneuvers and the use of the automated external defibrillator (AED) are the cornerstone for survival. Instruments that improve education would increase the responsiveness of lay personnel. Objectives: to develop, validate and evaluate a knowledge test on cardiopulmonary resuscitation and correct use of the automated external defibrillator in Asunción during 2023. Methodology: observational cross-sectional study, non-probabilistic sample for convenience of lay personnel users of mass attendance centers in Asunción. An exclusive questionnaire was developed on knowledge in cardiopulmonary resuscitation and the use of the automated external defibrillator (KOR-AED) based on the chain of survival in out-of-hospital cardiac arrest. Content, construct, and internal consistency were validated using expert opinion, factor analysis and Cronbach's alpha. Results: a total of 200 lay people participated, mostly shopping mall customers, with a predominance of men (63.5 %) (127), between 25-29 years old 28.5% (57). 61.5 % (123) had a university education, 75.5 % (151) had not related to health, 52 % (104) had prior knowledge of CPR, but 81.5 % (163) did not. The test showed reliability and suitability for factor analysis (Cronbach's alpha 0.75, Kaiser-Meyers-Olkin; 0.78, Bartlett p<0.05). The questions covered the first three links in the chain of survival, with items of medium to high difficulty. Women performed significantly better (p=0.04). Conclusion: the KOR-AED test is a valid and reliable instrument to improve the education of the layperson in CPR and use of the AED based on the chain of survival.