To test for randomization when Xi is binary,
A) you regress Xi, on all W's and compute the F-statistic for testing that all the coefficients on the W's are zero. (The W's measure characteristics of individuals, and these are not affected by the treatment.)
B) is not possible, since binary variables can only be regressors.
C) requires reordering the observations randomly and re-estimating the model. If the coefficients remain the same, then this is evidence of randomization.
D) requires seeking external validity for your study.
Answer: A) you regress Xi, on all W's and compute the F-statistic for testing that all the coefficients on the W's are zero. (The W's measure characteristics of individuals, and these are not affected by the treatment.)
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Henry David Thoreau faced a choice: Stay in the village of Concord or move out to Walden Pond. He decided to move to Walden. What was his" opportunity cost"?
A) There was no opportunity cost if he didn't pay rent for his cabin on Walden Pond. B) The satisfaction he would have enjoyed were he to stay in Concord C) The sweat and toil of building his own cabin and living off the land at Walden Pond D) There was no opportunity cost, because he made a free and voluntary decision to live the way he preferred to live.
In most places of the world, the marginal utility of water is low because
a. its supply is so abundant b. it is so essential c. it has so many uses d. total utility is so high e. it is very scarce