Refer to the Marine Technology (January 1995) study of major ocean oil spills by tanker vessels. The spillage amounts (thousands of metric tons) and cause of accident for 48 tankers are saved in the OILSPILL file. (Note: Delete the two tankers with oil spills of unknown causes.)
(a) Conduct an analysis of variance (at α = .01) to compare the mean spillage amounts for the four accident types: (1) collision, (2) grounding, (3) fire/explosion, and (4) hull failure. Interpret your results.
(b) Use Scheffe's method to rank the spillage ´ amount means of the four accident types. (Use an experimentwise error rate of α = .01.)