
Directions: Read carefully!
1. 
When working with the sampling distribution of a sample statistic, which of the choices would decrease the margin of error? 

Choose:


2. 
In an ecological study, the sampling mean proportion is 0.28 and the sample size is 50.
a) What is the margin of error with a confidence level of 95%?
Choose:
b) The researchers are 95% confident that the interval ____________ includes plausible values for the true proportion.
Choose:



3. 
Which choice is the margin of error, with a confidence level of 95%, for estimating the proportion of green mini M&Ms in a container, if 21 green mini M&Ms were drawn from the container in a random sample of 100 M&Ms? 



4. 
A researcher works on a study that has a population standard deviation of 0.73, a sample mean of 84.5, and a sample size of 60.
a) What is the margin of error with a confidence level of 95%?
Choose:



b) The researcher is 95% confident that the interval ____________ includes plausible values for the true mean.
Choose:


5. 
Situation: Times between use of TV remote by males during commercials.
• 95% confidence level
• n = 25
• = 5.25 seconds
• population normally distributed
• σ = 2.50 seconds
Which choice is the margin of error in this situation?
Choose:



6. 
A drug company is testing a new cold medication for children. The average child's cold symptoms last for 7 days. The company tested 500 children with a cold and found that 250 of them shortened their cold symptoms when taking the new drug. Assuming this to be a random sampling, would it be reasonable for the company to state that half of the children with a cold can decrease the lengths of their symptoms if they take this new drug? Explain. 


7. 
A study randomly surveyed 1,000 teenagers to determine if they had a TV in their bedroom. Surprisingly, 642 teens responded that they had a TV in their room.
a) Find a 95% confidence interval for the proportion of all teens who have a TV in their room.
b) If you change the confidence level to 90% (instead of 95%) explain how the confidence interval would change. 


8. 
A sample data set, n = 110, shows human body temperatures with a mean of 98.4ºF. If the standard deviation σ is known to be 0.65ºF,
a) find the margin of error for a 95% confidence level
b) find the confidence interval for μ.



9. 
Your guidance counselor informs you that a study shows that the average starting salary of college graduates who have taken a statistics course is $55,785. There were 35 people in the study and the standard deviation σ was $10,000. For a 95% confidence level, find the confidence interval for this study.



10. 
A sample of 60 bottlenose dolphins has a mean weight of 824 pounds. Assuming that σ is known to be 450 pounds, find a 99% confidence interval estimate of the mean of the population of all such dolphin weights.



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