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Problem 4

In 2022, a wildfire burned more than 10,000 acres in Isley, a small city on the edge of Florida’s Everglades. The fire damaged 89 homes, businesses, and other structures and caused over $42 million in damages. Wildfires require certain environmental conditions to spread, but the initial sparks sometimes come from electrical utility equipment and power lines. An investigation found that the origin of the Isley fire was a transmission tower, where one of the rows of hanging insulators had fallen to the ground. The insulators are designed to protect the tower from the electrical current flowing through the power lines, and they are hung with metal rings, called C-hooks. These C-hooks were manufactured by Seabyrd Iron Works, Inc, who claims that the hooks should not wear more than 5 mm over a fifty-year lifespan. In cooperation with the power company, an independent investigator was hired by the city of Isley to collect data on a random sample of the C-hooks at various transmission towers in the area. It was found that several of the hooks were eroding at a faster rate than was promised by the Seabyrd Iron Works when the local electric company purchased and installed them throughout their electric power system in the 1981.

The local utility company has blamed Seabyrd Iron Works, Inc. for manufacturing sub- standard parts that have worn prematurely. Civil litigation against the manufacturer has ensued, and a class-action lawsuit has been brought forth. In a class-action lawsuit, a certified group of individuals – a group called Isley Homeowners, in this case – sues the defendant for financial damages, claiming that the C-hooks provided in 1981 were not manufactured up to standard. The judge in this case has requested an impartial expert witness, and you have been brought in as a forensic engineer. Forensic engineers investigate the causes of failure in engineering projects ranging from faulty machinery to collapsed buildings. You will analyze the data the independent investigator collected and come to a statistically informed conclusion with a confidence level of 99% on whether the C-hooks used on transmission towers in Isley have already exceeded their promised wear of not more than 5.0 millimeters in 50 years.

The data provided by the independent investigator is below. Because it would be infeasible to test every C-hook in the area, eight transmission towers (labeled in the first column) were randomly selected, and the level of wear on the six C-hooks on each tower was measured. Does this sample data suggest that the average C-hook supplied by Seabyrd Iron Works has passed 5.0 mm in wear?

You will provide your findings in a memorandum addressed to the judge, Tanya Wasilew, and copied to the defense attorney, Mitch Soldano, and the plaintiffs' attorney Amira Herana. Remember that you are writing to convince the jury.