Which of the Following Are Probably Valid Criticisms of the Dickey

Multiple Choice

Which of the following are probably valid criticisms of the Dickey Fuller methodology?
(I) The tests have a unit root under the null hypothesis and this may not be rejected due to insufficient information in the sample
(ii) the tests are poor at detecting a stationary process with a unit root close to the non-stationary boundary
(iii) the tests are highly complex to calculate in practice
(iv) the tests have low power in small samples

A) (i) , (ii) , (iii) and (iv)
B) (i) , (ii) , and (iv) only
C) (i) and (iii) only
D) (ii) only