The variable the experimenter uses to create the treatment condition(s) is called the ___________ variable.

The variable that the experimenter manipulates to create different treatment conditions is referred to as the independent variable. This variable is fundamental in experimental research because it is the factor that is altered in an experiment to observe how it affects the dependent variable, which is measured for changes as a result of the manipulation. By varying the independent variable, researchers can assess its impact and determine causal relationships between variables.

In experimental designs, the independent variable is deliberately altered, while the dependent variable is observed and measured for any changes that result from those manipulations. Understanding which variable is being manipulated is crucial for interpreting the results of an experiment and establishing cause-and-effect relationships in the research.