[Campbell Biology P.800] If a hypothetical linear regression for hominin brain volume y vers... | Practice Question

If a hypothetical linear regression for hominin brain volume y versus age x yielded a slope m of 200 cm³/million years and a y-intercept b of 1350 cm³, what would be the expected mean brain volume for a hominin species that lived 3 million years ago x = -3 ?

  • A: 750 cm³
  • B: 1950 cm³
  • C: 1150 cm³
  • D: 1400 cm³

Explanation

The problem provides the linear regression equation form y = mx + b, along with hypothetical values for m slope , b y-intercept , and x age . The age '3 million years ago' corresponds to x = -3 as per the definition that negative values represent millions of years before the present . Substituting the values: y = 200 cm³/million years -3 million years + 1350 cm³ = -600 cm³ + 1350 cm³ = 750 cm³.