The test variable in Jeremiah's experiment is the water speed as the test variable in an experiment is the factor that is changed or manipulated by the person performing the experiment.
Jeremiah is actively manipulating the speed at which water flows down the tube to see how it affects the deposition of sand. This makes water speed the independent variable as it is the factor being controlled and changed.
By changing the water speed and observing its effect on sand deposition, Jeremiah can learn about the relationship between these two factors and gain a better understanding of the process of deposition.
complete question:
Jeramiah sets up an experiment to better understand the process of deposition. In his experiment, He places a pile of sand at the top of a tube. Then, he pours water down the tube at varying speeds. finally, he measures the amount of sand that is deposited throughout the tube. What is the test variable