Which action would increase the control of an experimental study?

Question

Quizplus · Accepted Answer

Establishing strict criteria for participant selection would increase the control of an experimental study by ensuring that the participants in both the experimental and control groups are similar in relevant demographic factors such as age, gender, education level, etc. This reduces variability and increases the likelihood that any observed differences between the groups are due to the manipulation of the independent variable and not some other factor. Allowing participants to decide whether or not to be in the experimental group (B) reduces control as it introduces self-selection bias. Ensuring that participants do not know the purpose of the experimental study (C) might increase control in some cases, but might also introduce demand characteristics. Increasing the number of assistants involved in data collection (D) might increase reliability and reduce measurement error, but does not necessarily increase control.

Which Action Would Increase the Control of an Experimental Study