Investigation 8: Gestation and longevity (assigned Fri Feb 5, due Wed Feb 10)

You may work with one other person on this assignment, handing in one report with both names. Word-processed reports are much preferred to hand-written ones. Please copy/paste relevant, well-labeled Minitab output into a Word file as appropriate.

The data in the Minitab worksheet mammals.mtw report the average gestation period (in days) and the average longevity (in years) for a variety of mammals.

a) Produce (and submit) a scatterplot of gestation period vs. longevity. Comment on the association between these variables as revealed in the plot.

b) Use Minitab to determine the regression equation for predicting gestation period from longevity. Plot this line on a scatterplot (and submit). Record this equation and the value of r². Comment on how well the line seems to describe the relationship between the variables.

c) Examine (and submit) a residual plot, and comment on what it reveals.

d) Take the logarithm (base 10) of each variable, and examine a scatterplot of log(gestation) vs. log(longevity). Does the relationship appear to be roughly linear?

e) Determine the regression equation for predicting log(gestation) from log(longevity). Also report the value of r². Then examine (and submit) a residual plot, and comment on what it reveals.

f) Use this regression equation to predict the gestation period for a species of mammal whose longevity is 12 years.

g) Use this model to predict the gestation period for the human species of mammal, whose longevity is about 75 years. Is your prediction reasonable? Explain.