In controlled experiments:
a. all variables are independent of each other.
b. all critical variables are manipulated.
c. all variables are dependent on each other.
d. one variable is manipulated while others are held constant.
e. all variables are held constant.
Ans: d. one variable is manipulated while others are held constant.
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Overall, water movement from the soil, through plant tissues, and finally to the atmosphere through transpiration, is driven by a gradient of
A) water potential. B) osmotic pressure. C) water temperature. D) specific leaf area.
Also known as seaweed, ___________________ algae are complex multicellular organisms that live mainly in salt water.
A. Brown B. Red C. Green D. Golden
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a) active uniport b) active antiport c) active symport d) passive symport e) passive antiport
Your first candidate for a regression to identify the effect of X1 on Y is: Yi = ?0 + ?1X1i + ?2X2i + Ui, where X2 is a control variable. Suppose a member of your consulting team suggests to you that another variable Ri should be a control that is also included in your regression, in order for you not to be worried about the endogeneity problem. What condition could you credibly test using data on Y, X1, X2, and R which could justify the inclusion of Ri as a control in your regression?
A. spcorr(Ri, Yi (Xi1, Xi2)) ? 0 B. Ri is exogenous. C. Ri has a strong correlation with X2. D. Ri has no effect per se on Yi.