Exam 10: Assessing Preventive and Therapeutic Measures: Randomized Trials

Participants in a clinical trial might report different symptoms when they know they are part of the intervention group instead of the control group.To avoid that,researchers use the following:

In a clinical trial,sometimes patients agree to receive an intervention but later decide to stop taking the medication.Moreover,some patients who were assigned to placebo decide to stop taking the placebo pill and buy the drug on their own (even when they do not know that they are taking a placebo pill).When this happens,researchers typically do the analysis according to the original assignment of the treatment regardless of the actual treatment received.What is the name of this procedure to analyze the data?

In a clinical trial,researchers might influence the selection of participants into a group (intervention or control),hence introducing bias into the study.What can be done to prevent from this threat to the validity of the study?

Two similar drugs (drug A and drug B) to alleviate back pain were released simultaneously.An investigator decides to test which of the drugs works better.He decides to conduct a trial in which randomly,half of the participants receive drug A for a month while the other half received drug B.After 2 weeks without any medication,participants switch the drug they were receiving (those who received A start taking B,and those who received B start taking A).What type of study design was illustrated in this example?