Variable control is a fundamental concept in scientific experiments that ensures only one factor is changed at a time while all other conditions remain constant. This helps researchers determine the specific effects of that variable on the outcome of the experiment. For example, in a study examining the impact of light intensity on plant growth, the type of plant, soil, and water must be kept the same to accurately assess how changes in light affect growth. By controlling variables, scientists can reduce the influence of external factors, leading to more reliable and valid results. This practice is essential in fields like psychology, biology, and chemistry, where understanding cause-and-effect relationships is crucial for drawing meaningful conclusions from experimental data.