Chapter 13 Experiments and Quasi-Experiments 13.1 Multiple Choice 1) The following are reasons for studying randomized controlled experiment in an econometrics course, with the exception of A) at a conceptual level, the notion of an ideal randomized controlled experiment provides a benchmark against which to judge estimates of causal effects in practice. B) when experiments are actually conducted, their results can be very influential, so it is important to understand the limitations and threats to validity of actual experiments as well as their strength. C) randomized controlled experiments in economics are common. D) external circumstances sometimes produce what appears to be randomization. Answer: C 2) Program evaluation A) is conducted for most departments in your university/college about every seven years. B) is the field of study that concerns estimating the effect of a program, policy, or some other intervention or “treatment.” C) tries to establish whether EViews, SAS or Stata work best for your econometrics course. D) establishes rating systems for television programs in a controlled experiment framework. Answer: B 3) In the context of a controlled experiment, consider the simple linear regression formulation Yi = β0 + β1 Xi + ui. Let the Yi be the outcome, Xi the treatment level, and ui contain all the additional determinants of the outcome. Then A) the OLS estimator of the slope will be inconsistent in the case of a randomly assigned Xi since there are omitted variables present. B) Xi and ui will be independently distributed if the Xi be are randomly assigned. C) β0 represents the causal effect of X on Y when X is zero. D) E(Y X = 0)is the expected value for the treatment group. Answer: B 4) In the context of a controlled experiment, consider the simple linear regression formulation Yi = β0 + β1 Xi + ui. Let the Yi be the outcome, Xi the treatment level when the treatment is binary, and ui contain all the additional ^
determinants of the outcome. Then calling β1 a differences estimator A) makes sense since it is the difference between the sample average outcome of the treatment group and the sample average outcome of the control group. ^
B) and β0 the level estimator is standard terminology in randomized controlled experiments. C) does not make sense, since neither Y nor X are in differences. D) is not quite accurate since it is actually the derivative of Y on X. Answer: A 5) The following does not represent a threat to internal validity of randomized controlled experiments: A) attrition. B) failure to follow the treatment protocol. C) experimental effects. D) a large sample size. Answer: D
Stock/Watson 2e -- CVC2 8/23/06 -- Page 309
