Why would using two manipulated variables in an experiment not be wise? please answer.?

Question

What is you veiw?

thank you.

Answer 1

When preforming an experiment, it is best only to have 1 independent variable which you control in order to observe its effects. By doing this you know that all changes you observe result from the change in the 1 variable.
If you change two variables you do not know which change caused what result on the experiment, and to what degree.

For example,
lets say you are doing an example to study the height a ball will bounce.
The experiment could be preformed by dropping a ball from a height and then measuring how high it bounces. The one variable in this case would be the height you drop the ball from. However, lets say you added another variable....the type of ball. One your first try you dropped a tennis ball from height h1 and found it bounded back to height h1_b. On the next try, you dropped a bowling ball from height h2 and measured it to bounce back at height h2_b.
h1 does not equal h2
h1_b does not equal h2_b
How can you relate the effects of changing the drop height of a ball when you change ball types in between? You cannot, you changed two things which both effect the outcome, you do not know how much the bounce height was effected by the individual changes in ball type and drop height since the effects get added together and mixed up in the results..

Answer 2

It's better to isolate each variable in case the changes due to one variable confound the results from the other.

Answer 3

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