Tanker oil spills. Owing to several major ocean oil spills by tank vessels, Congress passed the 1990 Oil Pollution Act, which requires all tankers to be designed with thicker hulls. Further improve- ments in the structural design of a tank vessel have been proposed since then, each with the objective of reducing the likelihood of an oil spill and decreasing the amount of out?ow in the event of a hull puncture. To aid in this development, Marine Technology (January 1995) reported on the spillage amount and cause of puncture for 50 recent major oil spills from tankers and carriers. The data are saved in the OILSPILL ?le.

(a) Use a graphical method to describe the cause of oil spillage for the 50 tankers.

(b) Does the graph, part a, suggest that any one cause is more likely to occur than any other? How is this information of value to the design engineers?

(c) Now consider the data on spillage amounts (in thousands of metric tons) for 50 major oil spills. An SPSS histogram for the 50 spillage amounts is shown below. Interpret the his- togram.

(d) Descriptive statistics for the 50 spillage am- ounts are also shown on the SPSS histogram. Use this information to form an interval that can be used to predict the spillage amount for the next major oil spill.