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For the benefit of other Experts who may respond to your question, the Science Buddies Project Idea that Just-T is working on can be found here: http://www.sciencebuddies.org/science-f ... p016.shtml
My problem is that I can't figure out what the variables are? Independent variable? Dependent variable? Controlled variable?
Let me give you a brief overview of dependent, independent, and controlled variables. The independent variable is the thing that you purposely change. From reading you post and the Science Buddies Project Idea, it looks to me like your independent variable is, as you say in your post, the type of toy (interactive toys, different shaped toys, etc.). The dependent variable is the variable that changes in response to the independent variable. The dependent variable depends on the independent variable. It looks like you dependent variable is not necessarily your dog, but rather your dog's behavior/interest level. Controlled variables are things you keep the same in each experiment and in each trial. You list a few variables that you should control: the location of the test, the dog, and the number of toys. Some other variables that you might consider controlling are: the distance from the dog to the toys when you release him/her, the basket the toys are in, the time limit for all of the trials (see step 8 in the "experimental procedure" section of the Project Idea), and the time of day that you do the experiments. You should also take a look at step 15 of the "experimental procedure" for other ideas of variables to control.
For more information about variables, take a look at Science Buddies' guide to variables, found here: http://www.sciencebuddies.org/science-f ... bles.shtml
. If you don't understand the discussion found on that page, you may want to look at this page: http://www.sciencebuddies.org/science-f ... test.shtml
A good way to present your dependent, independent, and controlled variables is in a list. Here's an example list:
Independent Variable: the type of toy (interactive toys, different shaped toys, different textured toys, favorite four)
Dependent Variable: Harley's behavior as measured by his interest level
Controlled Variables: the location of the test, using the same dog, and the number of toys... (you can add other controlled variables to this list)
Good luck with your project; let us know if you have any more question!