Snow geese feeding trial. Botanists at the University of Toronto conducted a series of experiments to investigate the feeding habits of baby snow geese (Journal of Applied Ecology, Vol. 32, 1995). Goslings were deprived of food until their guts were empty, then were allowed to feed for 6 hours on a diet of plants or Purina Duck Chow.
For each of 42 feeding trials, the change in the weight of the gosling after 2.5 hours was recorded as a percentage of initial weight. Two other variables recorded were digestion efficiency (measured as a percentage) and amount of acid-detergent fiber in the digestive tract (also measured as a percentage). The data for selected feeding trials are listed in the table below.
(a) The botanists were interested in the correlation between weight change (y) and digestion efficiency (x). Plot the data for these two variables in a scatterplot. Do you observe a trend?
(b) Find the coefficient of correlation relating weight change y to digestion efficiency x. Interpret this value.
(c) Conduct a test to determine whether weight change y is correlated with a digestion efficiency x. Use α = .01.
(d) Repeat parts b and c, but exclude the data for trials that used duck chow from the analysis. What do you conclude?
(e) The botanists were also interested in the correlation between digestion efficiency y and acid-detergent fiber x. Repeat parts a-d for these two variables.