Which of the following is most likely to improve the external validity of a research study?

• A. Conducting the study in a highly controlled laboratory environment
• B. Increasing the number of control variables in the study
• C. Using a random sampling method to select participants from the target population
• D. Selecting participants who are all similar in age and background

Answer: (C)

Verified step by step guidance

1. Understand that external validity refers to the extent to which the results of a study can be generalized to other settings, populations, and times.
2. Recognize that conducting a study in a highly controlled laboratory environment often improves internal validity but may reduce external validity because it is less like real-world conditions.
3. Know that increasing the number of control variables helps control confounding factors, which improves internal validity but does not necessarily improve external validity.
4. Identify that selecting participants who are all similar in age and background limits the diversity of the sample, which reduces the ability to generalize findings to a broader population, thus lowering external validity.
5. Conclude that using a random sampling method to select participants from the target population increases the representativeness of the sample, thereby improving the external validity of the study.