When analyzing investigations, it is important to identify...
- the independent and dependent variables in an experiment.
- the hypothesis being tested when supplied with a description.
In an experiment we want to be able to say that only the independent variable affects the dependent variable. In order for this to be true, we need to make sure that all other variables that could affect the dependent variable are prevented and controlled. A variable that might affect an experiment but is prevented from doing so is called a constant.
A prediction about the effect of an independent variable on a dependent variable is called a hypothesis. Scientists want to be able to explain what has happened in their experiments, and so they make a prediction before they conduct the investigation.
Example of a Controlled Experiment
This experiment is designed to test the prediction that the more light plants receive, the taller the plants will grow. The independent variable is the amount of light, and it changes because you purposely change the light. The height of the plants is the dependent variable and it changes in response to the independent variable. All other factors in this experiment must remain the same. Some examples of these factors, or constants, are:
- All the plants are the same size.
- The same soil is used in each pot.
- The plants are watered at the same time each day.
- All the plants are given the same amount of water.
- All plants are kept in the same place.