When more than one variable in an experiment is changed at a time the scientist?

When more than one variable in an experiment is changed at a time, the scientist risks confounding the results, making it difficult to determine which variable is responsible for any observed effects. This lack of control can lead to misleading conclusions, as it becomes unclear how each variable influences the outcome. To ensure valid results, it's essential to isolate and manipulate one independent variable at a time while keeping others constant. This approach allows for clearer cause-and-effect relationships to be established.