1.30 Structurally deficient highway bridges. Refer to Exercise 1.29. The NBI dat

Question

1.30 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 defi- cent, 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?

Explanation / Answer

1.30

Reason for restricting to the ones above 20 feet is, for regular maintenance and updating of all the major bridges that carries the larger traffic.

1.14

Using the Random Numbers generator in R,

Since the range of observations is not specified, let us assume the range is from 1 to 100.

Code in R:

>sample (1:100,10)

which generates the 10 simple random numbers as follows:

79 82 58 34 30 52 6 3 81 90

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