In Which of the Following Examples Is the Independent Variable

Multiple Choice

In which of the following examples is the independent variable manipulated by the presence versus absence technique?

A) In one experimental condition teachers receive in-service training. In the other condition, the teachers receive no training.
B) In one experimental condition teachers receive in-service training. In the other experimental condition the teachers receive a written training document for study.
C) In one experimental condition, the teachers receive one day of in-service training. In the second condition, the teachers receive two days of training. In the third condition, the teachers receive three days of training.
D) In one experimental condition teachers receive in-service training from a college professor. In the second condition, the teachers receive in-service training from a peer.