An experimental question is a cause-effect question.
Note: Things that can be changed or change on their own are called variables.
In an experimental question, the variable that causes another variable to change is called the independent variable. The variable that is affected (caused to change) is called the dependent variable
For example:
In the question, “How does water affect plant growth?”
1. what has been affected? PLANT GROWTH
2. what is the cause of the plant growth? WATER
In the example experimental question, “How does water affect plant growth?,” the independent variable and dependent variable are too general.
Yes! There is one independent variable which is water, but the question needs to be more specific. Such as:
1. What is the source or kind of water? Tap water, distilled water, ocean water, lake water, etc….
2. How much water?
3. What is the temperature of the water?
Yes! There is one dependent variable which is plant growth, but the question needs to identify how this variable will be changed. Also, the question should identify the plant. Such as:
1. Changes in the height of a pinto bean plant?
2. Changes in the number of leaves on a pinto bean plant?
A good testable experimental question that identifies one specific independent variable and one specific dependent variable might be:
How does the amount of tap water affect the height of pinto bean seedlings?
The question points out one specific cause–AMOUNT OF TAP WATER–and what it will be affecting–height of pinto bean seedlings.
The question, “How do plants grow toward a light?,” is not an experimental question that could easily be determined. How this happens occurs inside the plant resulting in the stems bending toward the light and it is not something you could easily discover by experimenting. While the question does identify an effect–plants growing toward a light-the question does not identify a cause nor does it identify the type of plant or light source.
You could discover how different things (called variables) affect the plant’s growth toward light. In other words, the growth of the plant toward the light DEPENDS ON what variables?
Examples of variables that might CAUSE a plant’s growth toward light include, sources of light-sun, lamp, etc. color of the light, distance of the plant from the light, direct or indirect light– barriers, etc….
INDEPENDENT VARIABLES: Things that MIGHT CAUSE a plant to grow toward light.
DEPENDENT VARIABLE: A measurable effect of the independent variable. In other words, how to measure the results.
1. What affect does the amount of sunlight have on the rate pinto bean seedlings grow toward the light?
2. How does the color of artificial light effect the rate pinto bean seedlings grow toward the light?
Why are plants green?
* How does water move through a leaf?
* What are the parts of a flower?
