Question

A physical therapist is conducting a study on the effects of breathing exercises and quatic therapy on preoperative lunt function in in patients undergoing partial lobectomies. Subjects we randomized to one of four groups: control, breathing exercises aquatic therapy, breathing exercises and aquatic therapy. The pulmonary lung function is measured pre-operatively and modeled using MLR Y- Bo+B,XX + B,X,1 + B,X3/+* Y = pulmonary function X1... 1 if breathing only: 0 otherwise X21-1 if aquatic therapy only; 0 otherwise X31-1 if combination; otherwise 4. How would you interpret the coeficient Ba? 5. What contrast would you evaluate in order to compare the mean pulmonary function between the breathing exercise alone group and the combination (breathing exercise and aquatic therapy) group? O a. B1-B3 Ob.B2-B3 Oc. None Od. B1-B2

Answer 1

the coefficient Ba represents the change in mean pulmonary function for the group that received breathing exercises only (compared to the control group) holding all other variables constant.

to compare the mean pulmonary function between the breathing exercise alone group and the combination group you would evaluate the contrast B1-B3.
this would give you the difference in mean pulmonary function between the breathing exercise alone group and the combination group after controlling for the effects of aquatic therapy and the control group.