Chapters 9 and 10 Name:___________________________

1. USA Today ran a report about a University of NC poll of 1248 adults from the southern United States. It was reported that 8% of those surveyed believe that Elvis Presley still lives. The article began with the claim that "almost 1 out of 10" Southerners still thinks Elvis is alive. Is there enough evidence to support the claim that the true percentage of Southerners that believe Elvis is alive is less than 10% at =0.02?

• Check the conditions for normality
• Null Hypothesis:
• Alternative Hypothesis:
• Type of Test (Two tailed, Right tailed, Left Tailed):
• P-Value:
• Conclusion about the Null Hypothesis:
• Conclusion about the Claim:

2. In the first two months of a recent year, 94 car occupants were killed by air bags, and 61 of them were "improperly belted". Construct a 92% confidence interval estimate of the percentage of car occupants who were killed by air bags while being improperly belted. Also write a statement that interprets the confidence interval. (Be sure to check conditions for normality)

3. A NAPA Auto Parts supplier wants information about how long car owners plan to keep their cars. A simple random sample of 25 car owners results in a sample mean of 7.01 years and a sample standard deviation of 3.74 years. Assume that the sample is drawn from a normally distributed population.

• Construct a 99% confidence estimate of the population mean.
• Interpret the confidence interval.
• Past data records the population mean to be 8.07 years. Does your sample data support a claim that the population mean is less than 8.07 years now? Why or why not? Show your proof.

4. An article in Forbes magazine reported that 73% of Fortune 500 companies have Twitter accounts. An economist thinks the percentage is higher at technology companies. She samples 70 technology companies and finds that 55 of them have Twittter accounts. Can she conclude that more than 73% of technology companies have Twitter accounts using the = .05level of significance?

• Check the conditions for normality
• Null Hypothesis:
• Alternative Hypothesis:
• Type of Test (Two tailed, Right tailed, Left Tailed):
• P-Value: Conclusion about the Null Hypothesis:
• Conclusion about the Claim

5. The National Health Statistics Reports described a study in which a sample of 360 one-year-old baby boys were weighted. Their mean weight was 25.5 pounds with a standard deviation of 5.3 pounds. A pediatrician claims that the mean weight of one-year-old boys is greater than 25 pounds. Do the data provide convincing evidence that the pediatrician's claim is true?

• Check conditions for normality:
• Null Hypothesis:
• Alternative Hypothesis:
• Type of Test (Two tailed, Right tailed, Left Tailed)
• : P-Value:
• Conclusion about the Null Hypothesis:
• Conclusion about the Claim

6. A Pew poll surveyed 1802 Internet users and found that 829 of them had posted a photo or video online. Can you conclude that less than half of all Internet users have posted photos or videos online? Use the = .05 level of significance.

• Check conditions for normality:
• Null Hypothesis:
• Alternative Hypothesis:
• Type of Test (Two tailed, Right tailed, Left Tailed):
• P-Value:
• Conclusion about the Null Hypothesis:

7. A Harris poll surveyed 2016 adults and found that 423 of them had one or more tattoos. Can you conclude that the percentage of adults that have a tattoo is less than 25%? Use the = .01level of significance.

• Check conditions for normality:
• Null Hypothesis:
• Alternative Hypothesis:
• Type of Test (Two tailed, Right tailed, Left Tailed):
• P-Value:
• Conclusion about the Null Hypothesis:
• Conclusion about the Claim

8. The mean waiting time at the drive-through of a fast-food restaurant from the time an order is placed to the time the order is received is 84.3 seconds. A manager devises a new drive-through system that he believes will decrease wait time. He initiates the new system at his restaurant and measures the wait time for 10 randomly selected orders. The wait times are:

108.5, 67.4, 58.0, 75.9, 65.1, 80.4, 95.5, 86.3, 70.9, 72.0

Is the new system effective? Use = 0.1 level of significance.

• Check conditions for normality:
• Null Hypothesis:
• Alternative Hypothesis:
• Type of Test (Two tailed, Right tailed, Left Tailed):
• P-Value:
• Conclusion about the Null Hypothesis:
• Conclusion about the Claim: