Structurally deficient highway bridges. Refer to Exercise 1.29. The 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 608,272 highway bridges in the United States was categorized as structurally deficient, functionally obsolete, or safe. About 13.5% of the bridges were found to be structurally deficient, while 3.5% 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 NBI obtain the data for the study?

The variable that the researcher is interested in is thecondition of the highway bridges of the United States. These bridges can be classified as being structurally deficient or could be safe, or could be obsolete functionally.

The variable isqualitativesince it organizes the variables into different types; moreover, no numeric is involved. Therefore, the condition of highway bridges is a qualitative variable.

Each of the highway bridges of the United Nations, 608,272 highway bridges data was analyzed and then categorized into a category such as structurally defective, functionally outdated, or secure. All highway bridges are monitored and not just some group of highway bridges. Hence, the data is taken in fromthe population.

The NBI acquired the data byinspectionthat is done periodically for noting the structural deficiency of bridges. This assessment is undertaken by FHWA; this data is compiled and moved to NBI.