Clinical trials are divided into two groups of parallel and sequential controlled studies. This article explains the features related to parallel studies.
Parallel or concurrent controlled studies
In order to control the intervention in interventional studies, the researcher divides the participants into two groups. The first group receives the intervention, whereas the second group is subjected to the placebo. The experimental and control groups should be homogenous in terms of all the variables except for the intervention.
The best way to ensure the homogeneity of the variables and intervention is to conduct the study at a specific given time, which leads to the concurrent control study. One major aspect of parallel studies is to conduct double-blind trials, meaning that neither the researcher nor the participants know which participants belong to the control group and which belong to the experimental group.
Regarding the sample distribution, parallel studies can be categorized as randomized clinical trials and non-randomized clinical trials. Randomized clinical trials are studies in which participants are randomly assigned to the experimental and control groups. This type of randomization can provide accurate and unbiased results. On the other hand, non-randomized clinical trials are sometimes conducted as comparative or simple clinical trials since the participants are not randomly chosen. This type of study can be exposed to different types of biased judgments and provide lower predictive power, compared to randomized clinical trials.
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