So I am a bit confused as to which variable would be the response and which would be the explanatory. Here is the question:

U.S. car sales vary from month to month because of car prices, the national economy,the weather, etc. One potential factor from among these is gas prices. To explore this question, youwill analyze U.S. car sales data and gas price data from Jan. 2000 to June 2001. The variables are defined as follows:

  • Percentage (high mpg): Percentage of cars sold with mpg > 26.75. That is, Percentage (highmpg) = Sales (high mpg)/Total number of cars sold
  • Gas Price: Average price of regular gas (in cents)

Would the Gas Price be the explanatory and the Percentage (high mpg) be the response variable?