I. Importance and validity of the experiments

to. Give three branches in economics where experiments have been used and an example for each.

b. Explain econometrically and conceptually why the experimental method produces causal results on the effect of a treatment, T, on a variable, Y.

c. Explain what internal validity is and what external validity is

d. Briefly compare the internal and external validity of laboratory experiments vs. field (i.e., which tends to have more or less internal or external validity and why)

and. Two typical limitations of laboratory experiments