Answer
One cannot form a conclusion about the effect of one variable if others are not controlled because the cause of the results of the experiment would not be particularly known. If the point of the experiment is to find out what one variable does, and if other variables are not controlled, then you really cannot be sure if the results were caused by the variable you were considering or if the effects were caused by other variables that weren't being properly controlled.
Work Step by Step
One cannot form a conclusion about the effect of one variable if others are not controlled because the cause of the results of the experiment would not be particularly known. If the point of the experiment is to find out what one variable does, and if other variables are not controlled, then you really cannot be sure if the results were caused by the variable you were considering or if the effects were caused by other variables that weren't being properly controlled.
