Table 2 Comparison of the answers between cases and controls^a

  I think most of the time they are aware of what is happening in these studies

  I am aware they exist but I do not know their function

  I do not know what an Ethics Committee is

  I am aware that they exist but I am not sure if they fulfill their functions

  I think most of the time they are not aware of what is happening in these studies

  I am sure that most of the time they are not responsible of fulfilling their function

  Other opinion

  To ensure that research physicians and their collaborators are adequately qualified

  I do not know precisely what responsibilities they must fulfill

  To review whether the research study characteristics provide benefits to the participants

  To approve or deny permission to execute a research study

  To register the experimental drug’s adverse reactions as they occur

  To interrupt the research study in case they consider that participants could be at risk

  To make sure that the informed consent documents are easy to understand

  Other function

  They must be qualified physicians evaluated by international pharmaceutical companies

  I have no opinion on the matter because I do not know any research physician

  They are like any other physician, the only difference is that they do this activity

  I believe that most of them participate in this kind of studies only because of the money they are paid

  I think that they must not be very good physicians

  Other opinion

  It is much better than private medical care

  It must be the same as private medical care

  I do not know if it is better or worse than private medical care

  I believe the most important fact is that the medical care is free of charge

  It is inferior to private medical care

  Other reason

  Yes

  No

  Because participants receive closer follow-up than with any other medical center

  Because participants receive new treatments that offer more advantages than any other medication available

  Because international scientists are monitoring the medication’s effects

  Because these are very strict studies where all medical adverse reactions are monitored

  Because the physician is available and can be found easily

  Although it is not ideal, it is the best way to get medical care if you lack economical resources to pay for it

  Because they perform a lot of laboratory tests free of charge

  Because physicians that do medical research are more qualified

  Because of potential risks that are not present when using authorized treatments

  Because a lot of unnecessary laboratory tests are performed

  Because treatments are interrupted once the research study is over

  Because they require you to assist to a lot of unnecessary consults

  Did not answered

  Other reason

  Yes

  No

  There should not be monetary supportive stimuli unless they are strictly justified

  That it is necessary in order to cover the costs of extra transportation that participating in a study implies

  I think it is payment for risking my health

  Other reason

  I think it is a good payment for participating in a research study

  I think it is used to convince some people to enroll in a research study

  Monetary supportive stimuli are not proportionate to the potential risks that participating in a research study implies