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What's a control?

I'm doing a science experiment on what type of juice cleans a dirty penny the best. You see, this is my second time being in a science contest, and last year I didn't need a control. This is the first time I've actually had to DEAL with the problem. I've asked my teachers, looked it up, and although I'm smart, I can be VERY slow when it comes to science. So, to summarize it all up, what's a control?
P.S. Please make the explanation really simple!

Jasmine D
- Woodbride, Virginia
January 19, 2010

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January 21, 2010

Hi, Jasmine. "Rigor" is a crucial part of education and learning. Making it too easy on yourself is only pretending that you are learning to think deeply; it's like telling yourself you will train for a marathon while keeping it easy by only walking a block :-)

But a "control" is some object and/or procedure that tries to duplicate the effect of everything except what you are checking for so that you can demonstrate causal relationship to yourself. Suppose you usually stay up 'til 1 AM every night watching TV before you start your hour of homework, and you always find yourself tired in school. If you believe that the hour of homework is what is making you so fatigued, you could skip the homework for a few nights and just stay up to 2 AM watching TV and see if you are still tired the next day. Staying up 'til 2 without actually doing the homework is the control.

Of course, your parents might demand a different control like seeing if you are still tired the next day if you start your homework at 9 PM and are in bed by 10. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey