Polychlorinated biphenyls (PCBs), industrial pollutants, are known to be a great danger to natural ecosystems. In a study by R. W. Risebrough titled “Effects of Environmental Pollutants Upon Animals Other Than Man” (Proceedings of the 6th Berkeley Symposium on Mathematics and Statistics, VI, University of California Press, pp. 443-463), 60 Anacapa pelican eggs were collected and measured for their shell thickness, in millimeters (mm), and concentration of PCBs, in parts per million (ppm).
a) Obtain a scatterplot for the data.
b) Decide whether finding a regression line for the data is reasonable. If so, then also do parts (c)–(f).
c) Determine and interpret the regression equation for the data.
d) Identify potential outliers and influential observations.
e) In case a potential outlier is present, remove it and discuss the effect.
f) In case a potential influential observation is present, remove it and discuss the effect.