The nbi data were analyzed and the results made available oat the fhwa web site. using the fhwa inspection rations, each of the 599,766 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, while 13.5% 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?