I need help with my independent variable.
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eighth grader
- Posts: 1
- Joined: Wed Oct 10, 2007 6:10 am
I need help with my independent variable.
I am doing my science fair project on plant tropisms. "How does gravity, water, and light affect the direction of plant growth?" is my experiment question but my teacher didn't agree with my independent variable.
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wildfirefox
- Former Expert
- Posts: 45
- Joined: Tue Oct 02, 2007 3:27 pm
You teacher doesn't agree with you because you have multiple independent variables. You have:
1. Gravity
2. Water
3. Light
For one thing, gravity is always constant. Unless you have a gravitational generator (a machine that manipulates gravity) or having access to a lab that is 3 miles above the earth surface, the gravity experiment is unless.
Water and Light are two great independent variables. You can use light as the independent variable, and introduce water as dependent variables. light and water work together in the process called photosynthesis. One will effect the other. Do a bit of research on that process. On top of that, select one as your independent variable.
1. Gravity
2. Water
3. Light
For one thing, gravity is always constant. Unless you have a gravitational generator (a machine that manipulates gravity) or having access to a lab that is 3 miles above the earth surface, the gravity experiment is unless.
Water and Light are two great independent variables. You can use light as the independent variable, and introduce water as dependent variables. light and water work together in the process called photosynthesis. One will effect the other. Do a bit of research on that process. On top of that, select one as your independent variable.
Those who can see that do not exist are geniuses. Those who can see what exists are brilliant. Those cannot see what exists are ignorant.
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Sareena Avadhany
- Former Expert
- Posts: 163
- Joined: Fri Oct 21, 2005 10:15 pm
Hi eighth grader,
I agree with wildfirefox that you have too many variables that you are dealing with. Variables are basically factors in your experiment that either can be manipulated or controlled, or respond to a stimulus or change in the environment.
You independent variable is a factor that you change to see its effect on your experiment. Your dependent variable is a factor that you cannot control, but responds to that manipulation.
Controls are factors in your experiment that you need to control, because if you don't, then you can never prove/disprove your hypothesis. This means you are introducing certain things that could potentially effect your results.
I'll use your project idea as an example:
Question: How does light effect plant growth?
Variables:
Independent and dependent: The amount of light exposed to the plant affects the rate of growth of the plant
Control: Temperature, Size of the plant box, amount of water for each plant, etc.
Now let's say we remove temperature from the control list. What would happen if, for one of your set-ups, the temperature was too cold, and all your plants died? What would you conclude? The problem is, you don't know if was the intensity of light or temperature of the environment that caused the death of your plants. You introduced a variable that was not related to your project.
Pursuing this question would be difficult, because it is more like 3 experiments instead of one. You should choose one factor, and test it. Variables are the most important things to consider when designing your experiment.
Hope this helps!
Sareena
I agree with wildfirefox that you have too many variables that you are dealing with. Variables are basically factors in your experiment that either can be manipulated or controlled, or respond to a stimulus or change in the environment.
You independent variable is a factor that you change to see its effect on your experiment. Your dependent variable is a factor that you cannot control, but responds to that manipulation.
Controls are factors in your experiment that you need to control, because if you don't, then you can never prove/disprove your hypothesis. This means you are introducing certain things that could potentially effect your results.
I'll use your project idea as an example:
Question: How does light effect plant growth?
Variables:
Independent and dependent: The amount of light exposed to the plant affects the rate of growth of the plant
Control: Temperature, Size of the plant box, amount of water for each plant, etc.
Now let's say we remove temperature from the control list. What would happen if, for one of your set-ups, the temperature was too cold, and all your plants died? What would you conclude? The problem is, you don't know if was the intensity of light or temperature of the environment that caused the death of your plants. You introduced a variable that was not related to your project.
Pursuing this question would be difficult, because it is more like 3 experiments instead of one. You should choose one factor, and test it. Variables are the most important things to consider when designing your experiment.
Hope this helps!
Sareena
Hello eighth grader!
I'm pretty sure the experts above me have provided you with the important information you need, but I will add something just to clarify it for you.
First of all, make sure you understand the difference between the different types of variables: independent, dependent, and controlled. An independent variable is one that you would like to change, and the dependent variable is the response to the change of the independent variable. A controlled variable is the variable that you would like to keep constant. Additional information can be found on the Science Buddies Homepage (https://www.sciencebuddies.org/mentorin ... bles.shtml).
As for your topic, it seems like you would have multiple independent variables, as wildfirefox said. Water and light are considered independent because they can be changed, while gravity cannot be changed and is therefore not an independent variable. Try to choose just one independent variable, either water or light. Also, for controlled variables, make sure you keep everything that you don't want to be changed in the experiment constant, such as the variables that Sareena Avadhany mentioned. Are you using more than one plant in your experiment (one for each amount of light/water)? If you are, than an example would be that each plant should have the same amount of soil, since this is a variable that is not being changed.
Good luck!
I'm pretty sure the experts above me have provided you with the important information you need, but I will add something just to clarify it for you.
First of all, make sure you understand the difference between the different types of variables: independent, dependent, and controlled. An independent variable is one that you would like to change, and the dependent variable is the response to the change of the independent variable. A controlled variable is the variable that you would like to keep constant. Additional information can be found on the Science Buddies Homepage (https://www.sciencebuddies.org/mentorin ... bles.shtml).
As for your topic, it seems like you would have multiple independent variables, as wildfirefox said. Water and light are considered independent because they can be changed, while gravity cannot be changed and is therefore not an independent variable. Try to choose just one independent variable, either water or light. Also, for controlled variables, make sure you keep everything that you don't want to be changed in the experiment constant, such as the variables that Sareena Avadhany mentioned. Are you using more than one plant in your experiment (one for each amount of light/water)? If you are, than an example would be that each plant should have the same amount of soil, since this is a variable that is not being changed.
Good luck!