Final answer:
A control that does not have a source of data, such as a field or mathematical expression, is called a controlled variable in an experiment.
Step-by-step explanation:
A control that does not have a source of data, such as a field or mathematical expression, is a controlled variable in an experiment. In scientific experiments, controlled variables are parts of the experiment that do not change, serving as a basis of comparison to determine the effect of the independent variable.
For example, in an experiment testing the effect of temperature on plant growth, the controlled variable would be the amount of light, soil, and water provided to all plants, as these factors should remain constant for accurate comparison.
Therefore, a control that does not have a source of data is referred to as a controlled variable.