A cookie company decides to develop a new chocolate chip cookie. They decide to test three different recipes at once. What are the advantages of making more than
one prototype at a time?

Automobile fuel efficiency is often measured in miles that the car can be driven per gallon of fuel (mpg). heavier cars tend to have lower fuel efficiencies (lower mpg ratings). which variable (weight or fuel efficiency) is most naturally considered the explanatory (predictor) variable in this context?