Researchers at the University of Toronto conducted a series of experiments to investigate whether a commercially sold pet food could serve as a substitute diet for baby snow geese (Journal of Applied Ecology,Vol.32. 1995). Goslings were deprived of food until their guts I were empty, then were allowed to feed for 6 hours on i a diet of plants or Purina Duck Chow. For each feeding trial, 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 42 feeding trials are listed in the I table on page 517

a. The researchers were interested in the correlation between weight change (y) and digestion efficiency (x). I Plot the data for these two variables in a scattergram. Do you observe a trend?

b. On the SPSS printout on page 516, locate the coefficient of correlation relating weight change y to digestion efficiency x. Interpret this value.

c. Conduct a test (at α = .01) to determine whether weight change y is correlated with digestion efficiency x. (Note: The SPSS printout reports p-values for a test of the null hypothesis of zero correlation.)

d. Repeat parts b and c, but exclude the data for trials that used duck chow from the analysis. What do you t conclude?

e. The researchers were also interested in the correlation between digestion efficiency ('y) and acid-detergent fiber (x). Repeat parts a-d for these two variables.