Question

Use the following information to answer. Many surgeons play music in the operating room. Does the type of music played have an effect on the surgeons' performance? The report "Death Metal in the Operating Room" (NPR, Dec. 24, 2009, www.npr.org) describes an experiment in which surgeons used a simulator to perform a surgery. Some of the surgeons listened to music with vocal elements while performing the surgery, and others listened to music that did not have vocal elements. The researchers concluded that the average time to complete the surgery was greater when music with vocal elements is played than when music without vocal elements is played. Explain why it is important that the surgeons be assigned at random to the two music conditions.

Short answer

Random assignment of surgeons to the two music conditions is important to prevent bias and establish causality. It ensures both groups are equivalent at the beginning of the experiment, minimizing the chance that some uncontrolled factor (like skill level) might account for the observed difference in average surgery completion times.

Step-by-step solution

Understanding Random Assignment

In scientific experiments, random assignment is the process of assigning subjects randomly to different treatment groups. This method ensures that all participants have an equal opportunity to be assigned to any of the groups. For instance, in this particular exercise, the two groups are: surgeons who listen to music with vocal elements during surgery and those who listen to music without vocal elements during surgery.

Role of Random Assignment in Bias Prevention

Random assignment helps in preventing bias, as it eliminates the possibility of self-selection or researcher’s preference affecting the outcome of the experiment. If the assignment of the surgeons to the music conditions was not random, some confounding variable, such as a specific skill level, might be more prevalent in one group than in the other. Random assignment helps ensure the results are due to the type of music and not some other factor.

Importance of Random Assignment for Causality

Random assignment plays a crucial role in determining causality in experiments. It makes the groups equivalent at the beginning of the experiment. This allows for the conclusion that the music type is responsible for the difference in average surgery completion time, and not some other uncontrolled factor.