# answers to the 5 question quiz on slide 20

1. Interpret each coefficient:

Intercept: 20.9 Watts represent the energy expenditure 
  of birds of mass 260 g.
typeeBat: 2.86 Watts is the additional energy required by
  echolocating bat of mass 260g compared to a 260g-bird.
typenBat: 0.70 Watts is the additional energy required by
  non-echolocating bats of mass 260g compared to a 260g bird.

2. Interpret each slope coefficient:

I(mass - 260): 0.0678 Watts/g: the slope of energy expediture
  versus mass, for birds. For each additional gram, birds spend
  an additional 0.0678 Watts on average.
I(mass - 260):typeeBat 0.0218 Watts/g: adjustment of the slope
  of energy expenditure versus mass, for echolocating bats.
I(mass - 260):typenBat -0.0277 Watts/g: adjustment of the slope
  of energy expenditure versus mass, for non-echolocating bats.

3. Predict the energy for a 20 g echo-locating bat.

  20.94 + 0.0678*(20-260) + 2.861 + 0.0218*(20-260) = 2.287

4 Predict the energy for a 220 g bird.

  20.94 + 0.0678*(220-260) = 18.23

5 Predict the energy for a 420 g non-echo-locating bat.

  20.94 + 0.0678*(420-260) + 0.70 - 0.0277*(420-260) = 28.05