Final answer:
The random assignment of participants in a randomized controlled trial is true; it ensures that the only difference between study groups is the variable being investigated, which is critical for a sound experimental design. A control group receiving a placebo treatment and the practice of blinding are additional measures that help eliminate bias and isolate the treatment's effect.
Step-by-step explanation:
In a randomized controlled trial, random assignment of participants to study groups serves a critical function. The statement that the random assignment helps ensure that the only difference between the groups is the variable under investigation is true. Random assignment is designed to balance out any preexisting differences between the groups, ensuring that these differences do not confound the results of the experiment. This includes demographic variances, psychological states, or any other factors that could influence the study's outcome.
The utilization of a control group that receives a placebo is also a standard practice in these trials. This group is essential for distinguishing the effects of the treatment from other potential effects such as the placebo effect or the power of suggestion. To enhance the validity of the findings, studies often use a double-blind design, where neither the participants nor the researchers know who receives the actual treatment or the placebo, thus minimizing bias.
Conclusively, the process of random assignment in experimental design is integral to ensure that the only impactful variable on the study's outcome is the one being directly manipulated by the researchers, known as the independent variable.