You want to study the things that affect depression. You want to see if depression is changed by the number of hours of therapy that a person does. So, you survey n=100 people who are currently in...

You want to study the things that affect depression.  You want to see if depression is changed by the number of hours of therapy that a person does.  So, you survey n=100 people who are currently in therapy for depression, and you ask them two things: How many hours a month do you get therapy?  And, How bad is your depression on a scale of 1-50?  Then you try to see if there’s a relationship between hours in therapy and how severe someone’s depression is.  What kind of hypothesis test should you do?