Question

# 1. It is advertised that the average braking distance for a small car traveling at 65...

1. It is advertised that the average braking distance for a small car traveling at 65 miles per hour equals 120 feet. A transportation researcher wants to determine if the statement made in the advertisement is false. She randomly test drives 36 small cars at 65 miles per hour and records the braking distance. The sample average braking distance is computed as 114 feet. Assume that the population standard deviation is 22 feet. a. H0: average breaking distance for small car traveling at 65 miles per hour = 120 feet H1:  average breaking distance for small car traveling at 65 miles per hour > 120 feet. b .H0: average breaking distance for small car traveling at 65 miles per hour ≠ 120 feet H1:  average breaking distance for small car traveling at 65 miles per hour = 120 feet   c. H0: average breaking distance for small car traveling at 65 miles per hour = 120 feet H1:  average breaking distance for small car traveling at 65 miles per hour < 120 feet d. H0: average breaking distance for small car traveling at 65 miles per hour = 120 feet. H1: average breaking distance for small car traveling at 65 miles per hour ≠ 120 feet

2. According to the Centers for Disease Control and Prevention (February 18, 2016), 1 in 3 American adults don’t get enough sleep. A researcher wants to determine if Americans are sleeping less than the recommended 7 hours of sleep on weekdays. He takes a random sample of 150 Americans and computes the average sleep time of 6.7 hours on weekdays. Assume that the population is normally distributed with a known standard deviation of 2.1 hours. a.H0: average sleeping hours of adults > 7 hours H1: average sleeping hours of adults < 7 hours

b.H0: average sleeping hours of adults = 7 hours H1: average sleeping hours of adults > 7 hours

c.H0: average sleeping hours of adults < 7 hours H1: average sleeping hours of adults = 7 hours

d.H0: average sleeping hours of adults = 7 hours H1: average sleeping hours of adults < 7 hours

A study by Allstate Insurance Co. finds that 82% of teenagers have used cell phones while driving (The Wall Street Journal, May 5, 2010). In October 2010, Massachusetts enacted a law that forbids cell phone use by drivers under the age of 18. A policy analyst would like to determine whether the law has decreased the proportion of drivers under the age of 18 who use a cell phone.

if the conclusion of hypothesis test is "reject H0", then which one is the correct implication of the

conclusion?

 a. There is evidence that proportion of teenagers who used cell phones while driving is decreased from 82%. b. There is evidence that proportion of teenagers who used cell phones while driving is different from 82%. c. There is no evidence that proportion of teenagers who used cell phones while driving is decreased from 82%. d. There is evidence that proportion of teenagers who used cell phones while driving is increased from 82%.

Customers at Costco spend an average of \$130 per trip (The Wall Street Journal, October 6, 2010). One of Costco’s rivals would like to determine whether its customers spend more per trip. A survey of the receipts of 25 customers found that the sample mean was \$135.25. Assume that the population standard deviation is \$10.50 and that spending follows a normal distribution.

a.Specify the null and alternative hypotheses to test whether average spending at the rival’s store is more than \$130.

if the conclusion of hypothesis test is "do not reject H0", then which one is the correct implication of the

conclusion?

 a. There is no evidence that average spending at the rival's store is \$130. b. There is no evidence that average spending at the rival's store is more than \$130. c. There is evidence that average spending at the rival's store is more than \$130. d. There is evidence that average spending at the rival's store is \$130.

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