Aerial survey methods are used to estimate the number of snow geese in their summer range areas west of Hudson’s Bay in Canada. To obtain estimates, small aircraft fly over the range and, when a flock of snow geese is spotted, an experienced observer estimates the number of geese in the flock. To investigate the reliability of this method, an experiment in which an airplane carried two observers flew over 45 flocks, and each observer independently estimated the number of geese in the flock. Also, a photograph of the flock was taken so that an exact count of the number in the flock could be obtained (Weisberg 1985). The data are contained in the file geese.
a. Draw scatterplots of observer counts, Y , versus photo count, x.Dothese graphs suggest that a simple linear regression model might be appropriate?
b. Calculate the linear regressions. What are the residual standard errors, what do they mean, and how do they compare? Do the fitted regressions appear to be different? Plot residuals and absolute values of residuals versus photo counts. Do the residuals indicate any systematic misfit? Does the residual variation appear to be constant?
c. Repeat the above using the square root transformation on the counts. Does this transformation stabilize the variance?
d. You have now computed the fits in two ways. How do they compare?
e. Write a few sentences in answer to the questions, “How well do observers estimate the number of geese?” “How o the two observers compare?”
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