VARIABLES

    The most important things to know when you design your experiment is what are your controls and variables. There are different types of variables. Listed below are explanations and examples.
 

MANIPULATED VARIABLES:

These are variables that you change on purpose in your experiment. It is what you are testing.
 

RESPONDING VARIABLES:

These are the changes that happen in your experiment because of what you changed
                                                              .

CONSTANT VARIABLES:

These are the variables that are held constant or are assumed to stay the same
during the experiment.
 
 

 

EXAMPLES

In a science project that would investigate "What is the effect of changing soil pH on plant growth," here are some examples of the different types of variables.
 

MANIPULATED VARIABLES:

pH. Probably the water that is used to nourish the plants will have chemicals added to it.  A wide range of pH is good to use.
 

RESPONDING VARIABLE:

Plant growth. You might determine plant growth by measuring the height of the plant, thickness of the stem, and/or the number of leaves before and during the experiment.
 

CONSTANT VARIABLES:

Temperature, Light, Type of Plant, and Type of Soil would all be variables that you should keep the same for all the plants for the whole time of the experiment.  If possible, you should also record values for these variables- what is the temperature, what is the amount of light, and for how long, etc... .
 

 

 

GRAPHING RESULTS

In displaying your results in a graph, the manipulated variable always goes across the bottom on the x-axis and the responding variable always goes up the y-axis. The values of the constant variables are not actually graphed but can be stated in the legend for the graph. This type of graph is always a line graph. Remember that a line graph shows change. A bar graph shows a comparison between things. If the project above used different types of plants and soils, bar graphs could also be done to compare one type of plant to another or one type of soil to another.
 

 

EXAMPLES:

 

Data Chart

 

Line Graph