5 (a.b.)  Manipulated Variable

A hypothesis (plural: hypotheses) is a possible explanation for a set of observations or answer to a scientific question.  In science, a hypothesis must be testable. This means that researchers must be able to carry out investigations and gather evidence that will either support or disprove the hypothesis. The one variable that is purposely changed to test a hypothesis is called the manipulated variable (also called the independent variable). The factor that may change in response to the manipulated variable is called the responding variable (also called the dependent variable).  An experiment in which only one variable is manipulated at a time is called a controlled experiment.