Science Buddies: "Ask an Expert"

Im a 9th grade advanced student. the title of my science fair project is "the effect of overpopulation on guppies". can u help me find out what my: Dependent variable, Independent Variable, and Control are.
Thank you.

Hi,

We can help you but you need to give us more information. What is your hypothesis? What 'effect' are you planning to measure and how will you do it. The effect that you measure is your dependent variable because it depends on the conditions that you set up, which in this case might be the number of guppies per gallon of aquarium water.

When you post a question to the Ask an Expert forum, please take the time to explain the idea behind your project and the experiments you plan to do. Otherwise we have to guess what you are doing and can't help you very well.

Sybee

Hi Leila,

Is this the project you are doing? http://www.education.com/science-fair/a ... n-guppies/

If so, your dependent variables are the behavioral changes you measure. The independent variable is the number of guppies ("population size"). Here is some more information about variables: https://www.sciencebuddies.org/science- ... bles.shtml

I hope this helps. As SciB said, it helps us Experts if you post more details about your project. Then we can provide more specific advice. Please post again (in this same thread) if you have more questions.

Heather

Thank you, and I also need help with the control of my project.

Hi Leila,

Remember that a control is a standard for comparison, so your control would be kind of the factor that stays constant (in a way, the "normal" for your setup), so you can compare all tests to the normal. The ScienceBuddies website has excellent resources on identifying variables and controls, so make sure to check it out!

Hi Leila,

ScibuddyAK gave you some great advice. There are two different ways to think about a control. One is a control treatment, which is the treatment that most represents the "normal" situation. In your project, it is probably the treatment with fewer guppies (less crowded). You can also have control variables, which are variables that stay the same between treatments. Ideally, you will do your best to keep everything the same between your treatments except for the experimental variable (number of guppies). So, in your case, control variables can include type of water (e.g., tap water), temperature of the water, how often the fish are fed, etc.

I hope this helps!

Heather