How To conduct a fair experiment what must a scientist do?

To conduct a fair experiment, a scientist must control variables to ensure that only the independent variable is tested while keeping all other conditions constant. They should also use a sufficient sample size to ensure results are statistically significant and repeatable. Additionally, the scientist should employ randomization to eliminate bias and maintain objectivity throughout the experiment. Lastly, documenting the methodology and results transparently is crucial for validating findings and allowing for peer review.