1. The National Highway Traffic Safety Administration (NHTSA) conducted a survey

Question

1. The National Highway Traffic Safety Administration (NHTSA) conducted a survey to learn about how drivers throughout the United States are using seat belts. Sample data consistent with the NHTSA survey are as follows Region Northwest Midwest South West Total Drivers use seat belt 148 162 296 252 Drivers do not use seat belt 52 54 74 48 228 For the United States, what is the probability that a driver is using a seat belt? The seat belt usage probability for a U.S. driver a year earlier was 0.75. NHTSA chief had hoped for a 0.78 probability in 2003. Would he have been pleased with the 2003 survey results? a. b. c. What is the probability of seat belt usage by region of the country? What region has the highest seat belt d. What proportion of the drivers in the sample came from each region of the country? What region had the usage? most drivers selected? What region had the second most drivers selected?

Explanation / Answer

for above"

a)P(driver using a seat belt)=858/1086=143/181 =0.7901

b)

Yes as probability of using seat belt has exceeded the target set by NHTSA chief,

c)

P(seat belt use|Northwest)=148/200=0.74

P(seat belt use|Midwest)=162/216=0.75

P(seat belt use|Southwest)=296/370=0.80

P(seat belt use|west)=252/300=0.84

West has highest seat belt usage

d)

here P(Northest drivers)=200/1086 =0.184

P(Midest drivers)=216/1086 =0.199

P(South drivers)=370/1086 =0.341

P(West drivers)=300/1086 =0.276

South had most drivers selected,

West has second most drivers selected,

region use seat belt not use seat belt total northwest 148 52 200 midwest 162 54 216 south 296 74 370 west 252 48 300 total 858 228 1086

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