A researcher conducts a study to determine whether smiling affects students' interest in the course material. In her 8am Physiological Psychology...

A researcher conducts a study to determine whether smiling affects students’ interest in the course material. In her 8am Physiological Psychology course, she never smiles while teaching. In her 9am Physiological Psychology course, she smiles often while teaching. At the end of the semester, she gives students a questionnaire to assess the extent to which students liked the course material. The results showed that the 9am class liked the course material more than the 8am class.

What is the independent variable?

 What is the dependent variable?

 What is the confound?

 How could the confound be fixed?