All of the following conditions are necessary for an instrumental variable Z to be a valid instrument for X in the regression: Yi = ?0 + ?1Xi + Ui except for which condition?
A. Cov(Xi, Zi) ? 0
B. Cov(Xi, Yi) ? 0
C. Cov(Zi, Ui) = 0
D. None of these choices are correct.
Answer: B
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Fresh water is much more dilute than the cells of a fish, so the animal constantly takes in water at its gills. How would a freshwater fish osmoregulate?
A. drink seawater and use active transport at the gills to take up salt from the water B. drink seawater and use active transport at the gills to get rid of excess salts C. produce dilute urine and use active transport at the gills to take up salt from the water D. produce dilute urine and use active transport at the gills to get rid of excess salt from the water E. drink saltwater and produce dilute urine to rid itself of excess salt
Chylomicrons are formed in the epithelial cell layer of the GI tract.
a. true b. false
The proband in a pedigree is always heterozygous. Indicate whether the statement is true or false
Approximately 40% of all children with Down syndrome have congenital ____________________ defects.Fill in the blank(s) with the appropriate word(s)