Science Buddies: "Ask an Expert"

My puropse for this project is - Will low density golf balls go further than the more dense ones?
I was asked to find a control group and I can't find one. Can someone help me with this?

Hi Melinda,

You're right, it's not really clear what the "control" is, because in this case there probably really isn't a control group. Can you elaborate on your experimental design though?
In the case of an experiment in which you are applying a treatment of some kind (say dunking balls in water) your control would be un-treated (dry) golf balls. In this case you appear to be testing
golf balls of different inherent densities and comparing their performance when struck. This is fine but there is no "control" group just balls of different densities. If you have more than two densities you could say the densest balls are the control and the other groups of balls are the experimental groups, but this is a fairly meaningless distinction.

Cheers,
Colin

Hi, Melinda. You have already received excellent advice from Colin. I wanted to add on to the discussion.

Not all experiments require a control group. A control group is necessary if you want to study the effects on something when its environment has changed. However, the purpose of other experiments is to find an optimal solution. An example of this is how to make the best cookies. You would experiment with different temperatures, baking times, amounts of sugar, etc. There is no control group in this type of experiment.

Your experiment falls under this latter category. You are trying to optimize the distance a golf ball will travel, based on density. Think of your variables in the following categories:

Independent variable(s): The variable(s) that will have different levels to determine the optimal setting for your outcome
Dependent variable(s): The variable(s) or outcome that is affected by changing the independent variable
Controlled variable(s): Settings you set constant during your experiment so they don't have an effect on the outcome

Hopefully, your teacher will accept your experiment if you can explain the process in the above terms. Can you identify the different variables for your experiment? Be sure to write back if you have further questions / if you would like for us to confirm your variable selections.

Good luck!