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Confidence Intervals Quiz 2 (25 MCQs)

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1. A researcher wishes to determine the mean energy consumption of a new light bulb. She takes a random sample of 41 bulbs and determines that the mean consumption is 1.3 watts per hour with a standard deviation of 0.7. When constructing a 97% confidence interval, which would be the most appropriate value of the critical value?
2. What critical value t* is used in constructing a 99% confidence interval based on n = 12 randomly selected observations.
3. A recent study of 750 Internet users in Europe found that 35% of Internet users were women. What is the 95% confidence interval of the true proportion of women in Europe who use the Internet?
4. A person selects a random sample of 15 credit cards and determines the annual interest rate, in percent, of each one. The sample mean is 12.42 with a sample standard deviation of 1.3. It is desired to construct a 90% Confidence Interval.Find the Standard Error to three decimal places.
5. Use the margin of error, confidence level, and standard deviation $ \sigma$ to find the minimum sample, n, required to estimate an unknown population mean $ \mu$ .Margin of Error = $ 134Confidence level = 95% $ \sigma$ =$ 542
6. Use the t table to find the critical value.95% confident, sample size = 8
7. A random sample of 100 WHS students found that 53 of them were in possession of a pencil. What is the p-hat ( population proportion percentage) for this sample?
8. Which of the following is NOT a common confidence level?
9. A random sample of 9 refrigerators has a mean cost of $ 1263 and a standard deviation of $ 530.75. Construct a 90% confidence interval for the average cost of a refrigerator.
10. The 90% interval for a statistics test was given by 72 +-7. What is the lower bound for the interval?
11. A research group wishes to estimate the mean amount of time (in hours) that members of a fitness center spend exercising each week. They want to estimate the mean within a margin of error of 0.5 hours with a 95% level of confidence. Previous data suggests that the standard deviation of the population is 2.2. Which of the following is the smallest sample size they could use?
12. A random sample of 20 cupcakes found the interval for average calories to be (150, 350). Which is the correct interpretation of the 95% confidence interval?
13. In a survey of 250 Internet users, 195 have high-speed Internet access at home. Find a 90% confidence interval for the proportion of all Internet users who have high-speed Internet access at home.
14. A random sample of 42 textbooks has a mean price of $ 114.50 and a standard deviation of $ 12.30. Find a 98% confidence interval for the mean price of all textbooks.
15. An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.What is the point estimate?
16. An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.What is the point estimate?(that is the number before the $ \pm$ symbol)
17. Find the critical value, tc for c = 0.99 and n = 10.
18. Which of the following changes to a study would result in a smaller confidence interval?
19. Find the Critical Value( z*) for an 86% Confidence Level. Be careful.
20. Suppose an interval is (.62, .70). Margin of error =
21. Use the z table or your calculator to find the critical value (Z*) that corresponds to 92% confidence.
22. What is the alpha value for a 95% confidence level?
23. In a survey of 250 Internet users, 195 have high-speed Internet access at home. Find a point estimate for the proportion of all Internet users who have high-speed Internet access at home.
24. A nurse at a local hospital is interested in estimating the birth weight of infants. How large a sample must sheselect if she desires to be 99% confident that the true mean is within 4 ounces of the sample mean? Thestandard deviation of the birth weights is known to be 9 ounces.
25. Construct a 95% confidence interval:A random sample of 75 oak trees has a mean height of 62 ft. Assume a population standard deviation of 3.8 ft.
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