In scientific experimentation, what is essential to ensure results are credible?

Using controls is essential to ensure credible results in scientific experimentation because controls provide a baseline for comparison, allowing researchers to isolate the effects of the independent variable being tested. By including control groups that do not receive the experimental treatment or by keeping certain variables constant, scientists can determine if the changes observed in the experimental group are truly due to the manipulation of the independent variable. This helps eliminate alternative explanations and reduces potential bias, making the findings more reliable and valid.

In contrast, increasing sample complexity may introduce more variability and make it harder to draw clear conclusions. Randomizing variables can be important in reducing bias, but it does not specifically address the need for a baseline comparison, which is central to validating results. Limiting observations can lead to missing important data and trends, thus undermining the overall credibility of the experiment.