Díaz García, AlejandroJiménez Buedo, MaríaTeira Serrano, David2024-05-202024-05-202015https://hdl.handle.net/20.500.14468/15643Field trials and quasi-experiments are comparative tests in which we assess the effects of one intervention (or a set thereof) on a group of subjects as compared to another intervention on another group of similar characteristics. The main difference between field trials and quasi-experiments is in the way the interventions are assigned to the groups: in the former the allocation is randomized whereas in the latter is not. We are going to see first the different roles played by randomization in medical experiments. Then we discuss how controlled field trials, originating in psychology, spread to the social sciences throughout the 20th century. Finally, we will show how the idea of a quasi-experiment appeared around a debate on what constitutes a valid test and what sort of controls guarantee it.capítulo de libroField trialquasi-experimentrandomizationvaliditycausalitycontrolsbiasDonald Campbell