MATH 225N Week 6 Confidence Intervals Questions & Answers (Get an A)

On a busy Sunday morning, a waitress randomly sampled customers about their preference for morning beverages, Specifically, she wanted to … find out how many people preferred coffee over tea. The proportion of customers that … coffee was 0.42 with a margin of error 0.07. Construct a confidence interval for the proportion of customers that preferred coffee. 2. A company sells juice in 1quart bottles. In a quality control test, the company found the mean volume of juice in a random sample of … bottles was X = 31 ounces, with a marginal error of 3 ounces. ….. Construct a confidence interval for the mean number of ounces of juice bottled by this company. 3. Randomly … employees at an office … to take part in a survey about overtime. The office manager wanted to find out how many employees worked overtime in the last week. The proportion of employees that … worked overtime was 0.83, with a margin of error of 0.11. 4. A random sample or garter snakes … , and the proportion of snakes that were longer than 20 inches in length recorded. The measurements resulted in a sample proportion of p = 0.25 with a sampling standard deviation of Op = 0.05. ……. Write a 68% confidence interval for the true proportion of garter snakes that were over 20 inches in length. 5. The average number of onions needed to make French onion soup from the population of recipes is unknown. A random sample of … recipes yields a sample mean of x = 8.2 onions. Assume the sampling distribution of the mean has a standard deviation of 2.3 onions. ……. Use the Empirical Rule to construct a 95% confidence interval for the true population mean number of onions. 6. In a survey, a random sample of adults … whether a tomato is a fruit or vegetable. The survey resulted in a sample proportion of 0.58 with a sampling standard deviation of 0.08 … a tomato is a fruit. ……. Write a 99.7 confidence interval for the true proportion of number of adults … the tomato is a fruit. 7. A college admissions director wishes to estimate the mean number of students currently enrolled. The age of random sample of 23 students is … Assume the ages are approximately normally … Use Excel to construct a 90% confidence interval for the population mean age. Round your answer to 2 decimal places and use increasing order. ……. Use week 6 worksheet to get mean and SD. 8. Suppose that the scores of bowlers in a particular league follow a normal distribution such that a standard deviation of the population is 12. Find the 95% confidence interval of the mean score for all bowlers in this league using the … accompanying data set of 40 random scores. Round your answers to 2 decimal places using ascending order. 9. In the survey of 603 adults, 98 said that they regularly lie to people conducting surveys. Create a 99% confidence interval for the proportion of adults who regularly lie to people conducting surveys. Use excel to create the confidence interval rounding to …4 decimal places. 10. In a random sampling of 350 attendees at a minor league baseball game, 184 said that they bought food from the concession stand. Create a 95%confidence interval for the proportion of fans who bought food from the concession stand. Use excel to create the confidence interval rounding to 4 decimal places. 11. Suppose that the weight of tight ends in a football league are normally … such that sigma squared = 1,369. A sample of 49 tight ends was randomly … and the weights are … Use Excel to create a 95% confidence interval for the … mean weight of the tight ends in this league. Rounding your answers to 2 decimal places and using ascending order. (Have to get square root of 1369 which is 37). Population sample is yes . 12. Suppose heights, in inches of orangutans are normally … and have a known population standard deviation of 4 inches. A random sample of 16 orangutans is … a sample mean of 56 inches. Find the confidence interval of the population mean with a 95% confidence level. 13. The population standard deviation for the total snowfalls per year in a city is 13 inches. If we want to … 95% confident that the sample mean is within 3 inches of the true population mean, what is the minimum sample size that should … taken? 14. The population standard deviation for the body weights for employees of a company is 10 pounds. If we want to … 95% confident that the … sample mean is within 3 pounds of the true population mean, what is the minimum sample size that should … taken. 15. The length, in words, of the essays written for a contest are normally distributed with a population standard deviation of 442 words and an unknown population mean. If random sample of 24 essays is taken and results in a sample mean of 1330 words, find a 99% confidence interval for the population mean. Round to two decimal places. 16. Brenda wants to estimate the percentage of people who eat fast food at least once per week. She wants to create a 95% Confidence interval which has an error bound of at most 2%. How many people should … polled to create the confidence interval? 17. Suppose a clothing store wants to determine the current percentage of customers who are over the age of forty. How many customers should … the company survey in order to … 92% confident that the estimated (sample) proportion is within 5% of the true population proportion of customers who are over the age of 40? 18. Suppose the scores of a standardized test are normally …. If the population standard deviation is 2points, what minimum sample size is needed to … 90% confident that the sample mean is within 1 point of the true … population mean? … sure to round up to the nearest integer. 19. The number of square feet per house are normally … with a population standard deviation of 197square feet and an unknown population mean. If a random sample of 25 houses is taken and results in a sample mean of 1820 square feet, find a 99% confidence interval for the population mean. Round to 2 decimal places. 20. Suppose scores of a standardized test are normally … and have a known population standard deviation of 6points and an unknown population mean. A random sample of 22 scores is taken and gives a sample mean of 92 ……. Identify the parameters needed to calculate a confidence interval at the 98% confidence level. Then find the confidence interval. 21. Suppose scores of a standardized test are normally … and have a known population standard deviation of 6points and an unknown population mean. A random sample of 22 scores is taken and gives a …sample mean of 92 ……. What is the correct interpretation of the 95% confidence interval? 22. The weights of running shoes are normally distributed with a population standard deviation of 3ounces and an unknown population mean. If a random sample of 23 running shoes is taken and results in a … sample mean of 18 ounces, find a 90%confidence interval for the population mean. Round the final answer to two decimal places. 23. The germination periods, in days, for grass seed are normally distributed with a population standard deviation of 5days and an unknown population mean. If a random sample of 17 types of grass seed is taken and results in a sample mean of 52days, find a 80% confidence interval for the population mean. 24. The speeds of vehicles traveling on a highway are normally distributed with a population standard deviation of 7miles per hour and an unknown population mean. If a random sample of 20 vehicles is taken and … results in a sample mean of 60miles per hour, find a 98% confidence interval for the population mean. Round the final answer to two decimal places. 25. Suppose finishing time for cyclists in a race are normally distributed and have a known population standard deviation of 6minutes and an unknown population mean. A random sample of 18cyclists is taken and gives a sample mean of 146 ……. Find the confidence interval for the population mean with a 99% confidence level.