Refer to Exercise 1.14. The most recent NBI data were analyzed, and the results made available at the FHWA web site (www.fhwa.dot.gov). Using the FHWA inspection ratings, each of the nearly 600,000 highway bridges in the United States was categorized as structurally deficient, functionally obsolete, or safe. About 12% of the bridges were found to be structurally deficient, and 14% were functionally obsolete.

a. What is the variable of interest to the researchers?
b. Is the variable of part a quantitative or qualitative?
c. Is the data set analyzed a population or a sample? Explain.
d. How did the researchers obtain the data for their study?
e. Use a random number generator to determine which bridges to include in a random sample of 25 bridges selected from the 600,000 bridges.

Data from Exercise 1.14

All highway bridges in the United States are inspected periodically for structural deficiency by the Federal Highway Administration (FHWA). Data from the FHWA inspections are compiled into the National Bridge Inventory (NBI). Several of the nearly 100 variables maintained by the NBI are listed below. Classify each variable as quantitative or qualitative.