The ratio of DDE related to DDT to PCB concentrations
The ratio of DDE (related to DDT) to PCB concentrations in bird eggs has been shown to have a number of biological implications. The ratio is used as an indication of the movement of contamination through the food chain. The paper “The Ratio of DDE to PCB Concentrations in Great Lakes Herring Gull Eggs and Its Use in Interpreting Contaminants Data’’ [ Journal of Great Lakes Research (1998) 24(1): 12–31] reports the following ratios for eggs collected at 13 study sites from the five Great Lakes. The eggs were collected from both terrestrial-and aquatic-feeding birds.
a. Compute the mean and median for the 21 ratios, ignoring the type of feeder.
b. Compute the mean and median separately for each type of feeder.
c. Using your results from parts (a) and (b) comment on the relative sensitivity of the mean and median to extreme values in a data set.
d. Which measure, mean or median, would you recommend as the more appropriate measure of the DDE to PCB level for both types of feeders? Explain your answer.
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