Experimentation 101

Variables Independent Variable - The part of the experiment that the researcher changes. (Manipulated Variable) Dependent Variable - The part of the experiment that changes because of the changes in the independent variable. (Measured Variable) Control Variable - A part of the experiment that the researcher keeps constant at all times. Control variables that cannot be completely controlled lead to experimental error.

If, then hypothesis If the independent variable effects the dependent variable, then specific prediction. Example: If temperature has an effect on leaf color change, then exposing plants to low temperatures will result in changes in leaf color.

Groups Experimental Group(s) – Trial of the experiment in which, specific conditions are adjusted based on the independent variable. Typically there will be multiple “trials” an experiment to increase the range of the independent variable and the sample size of the experiment Control Groups Positive control – An experimental trial that produces a known positive result Negative control – An experimental trial that produces a known negative result.

A researcher is testing the growth rate of plants when exposed to differing amounts of light. What is the independent variable? What is the dependent variable(s)? What are some control variables that would be necessary for this experiment? What are some possible experimental groups? How could sample size be increased? What is a positive and a negative control for this experiment?