Emilio's teacher told his class that a controlled experiment's results are valid only if one factor in the experiment is changed and all the other factors remain constant. Why is this statement true?
A.
Changing several different factors in an experiment takes too much time.

B.
When only one factor is changed, you can be more certain that it caused the results.

C.
When only one factor is changed, you don't need to use a control.

D.
Changing several different factors in an experiment takes too many controls.

Question

Emilio's teacher told his class that a controlled experiment's results are valid only if one factor in the experiment is changed and all the other factors remain constant. Why is this statement true?
  A. 
Changing several different factors in an experiment takes too much time.

  B. 
When only one factor is changed, you can be more certain that it caused the results.

  C. 
When only one factor is changed, you don't need to use a control.

  D. 
Changing several different factors in an experiment takes too many controls.

eiwoh · Answer

Let's see....one second plz...

eiwoh · Answer

The answer is 
1)Changing several different factors in an experiment takes too many controls.

This means that for every factor that is changed you need a control which has all the other factors stable - but with many factors, this might be undoable.

eiwoh · Answer

Buuut.....it can also be 
2) - 
When only one factor is changed, you can be more certain that it caused the results. 
This is your best answer