11. The National Occupant Protection Use Survey (NOPUS) was conducted to provide

Question

11. The National Occupant Protection Use Survey (NOPUS) was conducted to provide probability-based data on motorcycle helmet use in the United States. The survey was con- ducted by sending observers to randomly selected roadway sites where collected data on motorcycle helmet use, including the number of motorcyclists wearing a Department of Transportation mpliant helmet (National Highway Traffic Safety Administra- tion website, January 7, 2010). Sample data consistent with the most recent NOPUS are shown below. Type of Helmet DOT-Compliant Region Noncompliant Northeast 96 Midwest South West 16 Total 170

Explanation / Answer

a. There are 350 motorcyclist who wear DOT-compliant helmet and 170 who do not. Therefore, adding both one gets 520 motorcyclists surveyed.

P(motorcyclists wearing DOT-compliant helmet)=# of motorcyclists wearing DOT-compliant helmet/# number of motorcyclists surveyed [using classical definition of probability, P(A)=number of counts in A/Total counts].

=350/520

=0.6731 (ans)

b. It is said that the sample data is consistent with the most recent NOPUS. Therefore, there is an 15% increase (0.63-0.48=0.15) in five years for motorcyclists wearing DOT-compliant helmet. The result display a slow progress so administration might be worried.

c. Use row marginals to compute the required probability.

P(motorcyclists wearing DOT-helmet in Northeast)=96/(96+62)=0.6076

P(motorcyclists wearing DOT-helmet in Midwest)=86/(86+43)=0.6667

P(motorcyclists wearing DOT-helmet in South)=92/(92+49)=0.6525

P(motorcyclists wearing DOT-helmet in West)=76/(76+16)=0.8261

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