Which of the following methods enhances the validity of a research study?

Using random sampling techniques is a fundamental method for enhancing the validity of a research study. When researchers use random sampling, they ensure that every individual in the target population has an equal chance of being selected for the study. This reduces the likelihood of selection bias, where certain individuals may be overrepresented or underrepresented, potentially skewing results. A representative sample drawn through random means allows for more generalizable findings, making it easier to apply conclusions from the study to the broader population.

In contrast, choosing a small sample size can lead to a lack of statistical power and may not accurately represent the population, while relying solely on personal observations introduces subjective biases and reduces the reliability of findings. Improvising the study design often results in inconsistency and unpredictability, which can compromise the rigor and reproducibility of the research. Thus, random sampling is a critical method for strengthening the study's validity and ensuring robust and credible results.