Because if you change more then one variable you won't know which variable changed the outcome of the experiment. Test one variable at a time or you'll be lost.
let's say you bought a new soap and new laundry detergent. All of a sudden you are having allergic reactions. Which one is the cause? Well if you had only bought one at a time you'd know.
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Because if you change more then one variable you won't know which variable changed the outcome of the experiment. Test one variable at a time or you'll be lost.
If you have two variables, how can you be sure that your outcome is influenced by one variable and not the other?
let's say you bought a new soap and new laundry detergent. All of a sudden you are having allergic reactions. Which one is the cause? Well if you had only bought one at a time you'd know.
Because if you change more than one you cannot determine which had an affect if any.