What is fair test when do we say an investigatory does not show fair testing?

A fair test in an investigation ensures that only one variable is changed while all other conditions remain constant, allowing for a clear cause-and-effect relationship to be established. An investigatory does not show fair testing if multiple variables are altered simultaneously, if there are uncontrolled factors influencing the results, or if the methods used are biased. This lack of control can lead to unreliable or invalid conclusions. Ensuring a fair test is crucial for the integrity and reproducibility of scientific findings.