In which of the scenarios can you reverse the dependent and independent variables while keeping the interpretation of the slope meaningful?
A.
As the number of cigarettes smoked in a day increases, the risk for lung cancer increases.
B.
As the age of an infant increases, the height of the infant increases.
C.
As the number of vehicles in a city increases, the amount of pollution in the city increases.
D.
As the concentration of salt in water increases, the density of water increases.
E.
As the number of calls made by a cell phone increases, the cell phone bill amount increases.

Question

In which of the scenarios can you reverse the dependent and independent variables while keeping the interpretation of the slope meaningful?
 A. 
As the number of cigarettes smoked in a day increases, the risk for lung cancer increases.
 B. 
As the age of an infant increases, the height of the infant increases.
 C. 
As the number of vehicles in a city increases, the amount of pollution in the city increases.
 D. 
As the concentration of salt in water increases, the density of water increases.
 E. 
As the number of calls made by a cell phone increases, the cell phone bill amount increases.

Mercury · Answer

a bit late, but remember that the independent variable (x-axis) causes the change in the dependent variable (y-axis). for example, for A, it makes sense that the # of cigarattes would be on the x-axis and the lung cancer risk would be on the y-axis, since cigarette smoking has a causal effect on lung cancer rates. however, it doesn't make sense to swap these. getting lung cancer doesn't *cause* people to smoke more or less. so you can eliminate A.

go through the other choices with this same logic. find the choice where the data still makes sense when the variables/axes are swapped.