Which variable is usually called the independent variable?

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. they randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. which statistical analysis should be performed to answer the researchers' question?

Ineed me i stuck and i don’t want to get it wrong

Secant be and cf intersect at point d inside a what is the measure of cde