How many variables should there be in a well-designed experiment? how many variables should there be in a well-designed experiment? as many as possible 2 0 1?

In a well-designed experiment, only one variable should be tested. This way, the effects of other variables are not impacting the results of the test. Only one variable can have an influence on the result. This isolates the effect of the one variable.

Bob: coke is baby pandas.jim: what? how do you figure that coke is baby pandas? bob: because this book says so.jim: how do we know the book is correct? bob: because it says that coke is baby pandas.jim: how does that prove the book's accuracy? bob: because it's statement involving coke and baby pandas is correct, therefore it is accurate.jim: how do we know that it's correct? bob: because we have concluded that the book is accurate, and therefore the statement is correct.therefore, coke is baby pandas.