Hello. I am running a t-test. 2 groups, group 1 is a area size of a vein before intervention and the second is a vein after intervention. Some decrease and some increase in area. I need to determine if these increase/decrease changes are significant. I tried student t-test type 2, tail 3. Question 1: Am I using the correct tail #? Question 2: How can I determine if the changes are significant? Thank you for your time.