Suppose that there are two students, John and Mary. John is assigned to be in the treatment group and Mary in the control group. The treatment is a tutoring program, where John will work with a one-on-one tutor for three hours each week. Mary receives no extra tutoring. Yor refers to the Mary's test scores and Py to John's, ?" is a dummy variable that takes on the value 1 if the person is in the treatment group and O if the person is in the control group. In this example, which of the following states of the world are directly observed? (Select all that apply.] OW T-1 Our-1 Submit You home wind O of 2 allempts Question 2 01/0 point (gracdad) Which of the following expressions captures the effects of tutoring on test scores that we would ideally like to be able to measure? O (YT- 1) -(X/)T - 1) and [YT-0) -(MT -0) O only (Vy (7 - 1). since John is the only one assigned to the treatment group O (W/T- 1) - (YT -0] and (X 7 - 1) -[V, T -0) (VWIT - 1) and ( V, T - 1) Submit Question 3 0.0/10 point (gracdad) Now suppose that you have a large set of children assigned via lottery to receive tutoring or not. Those in the treatment group receive tutoring and those in the control group do not. Which of the following gives the "treatment on the treated" effect for an outcome Y'? Let ?" denote treated group, (7 denote the control group, Y? denote potential outcome with treatment and Y"s' denote potential outcome without treatment. Submit You home wind Ool 2 allempts Question 4 00/10 paint (cradad) Which of the following correctly describes selection blas? ") Treatment effects are different across individuals in the treatment group There could be underlying differences between those in the treatment and those in the control groups The bias that is introduced when researchers select which outcomes to measure and include in econometric models