Random samples from two age groups of brides (200 brides under 18 years and 100 brides at least twenty years old) showed that 50% of brides in the under 18 group were divorced after 15 years, while 40% of brides in the 20 or older age group were divorced after 15 years. The difference between the two proportions is 0.10, with a
In a nationwide survey of n = 1,030 adults, 6% answered yes to the question "During the last year did anyone break into or somehow illegally get into your home or apartment?" A 95% confidence interval (using exact value for z* ) for the proportion of all Americans who had their homes broken into is?
A random sample of n = 9 men between 30 and 39 years old is asked to do as many situps as they can in one minute. The mean number is x bar = 26.2 and the standard deviation is s = 6. a) find the value of the standard error of the sample mean. b) find a 95% confidence interval for the population mean.
1. Suppose you want an 85 percent confidence level. What value would you use to multiply the standard error of the mean? 2. Dr. Patton is a professor of English. Recently he counted the number of misspelled words in a group of student essays. For his class of 40 students, the mean number of misspelled words was 6.05 and the s
In an ABCNews.com nationwide poll done in 2001, the proportion of respondents who thought that it should be illegal to use a hand held cell phone while driving a car was 69 %. The poll's sample was 1027. A) Find the value of the standard error of the sample proportion. B) Find a 90% confidence interval estimate of the po
Consider the trash bag problem. Suppose that an independent laboratory has tested trash bags and has found that no 30-gallon bags that are currently on the market have a mean breaking strength of 50 pounds or more. On the basis of these results, the producer of the new, improved trash bag feels sure that its 30-gallon bag will b
See attached file for full problem description. 1. A simple random sample of 40 items resulted in a sample mean of 25. The population standard deviation is = 5. a. What is the standard error of the mean, _ x ? b. At 95% confidence,
Calculation of Sample estimation, Confidence Interval and Margin of Error. See attached file for full problem description.
68. In a study, Germination and Emergence of Broccoli, conducted by the Department of Horticulture at Virginia Polytechnic Institute and State University, a researcher found that at 5°C, 10 seeds out of 20 germinated, while at 15°C, 15 out of 20 seeds germinated. Compute a 95% confidence interval for the difference between t
A certain brokerage house wants to estimate the mean daily return on a certain stock. A random sample of 17 days yields the following return percentages: 1.87 2.94 1.39 -1.29 -0.51 -2.9 -2.83 1.11 1.43 -1.88 0.79 -0.97 1.13 -1.13 -2.95 1.49 -1.57 If we assume that the returns are normally distributed, fi
The breaking strengths of cables produced by a certain manufacturer have a standard deviation of 82 pounds. A random sample of 150 newly manufactured cables has a mean breaking strength of 1950 pounds. Based on this sample, find a 95% confidence interval for the true mean breaking strength of all cables produced by this manufact
Part I. Suppose the coach of the football team wants to estimate the proportion of the population of fans who support his current starter lineup. The coach wants the estimate to be .04 of the true proportion. Assume a 99 percent level of confidence. The coach estimated the proportion supporting the current starter lineup to
A sample of size n = 14 is selected from a normal population to construct a 95% confidence interval estimate for a population mean. The interval was computed to be (7.82 to 9.64). Determine the sample standard deviation.
6. The heights of a random sample of 50 college students showed a mean of 174.5 cm and standard deviation of 6.9 cm. a) Construct a 98% confidence interval for the mean height of all college students. b) What can we assert with 98% confidence about the possible size of our error if we e
What do confidence intervals represent? Please help me understand confidence intervals.
A biologist has found the average weight of 12 randomly selected mud turtles to be 8.7 lb with standard deviation 3.6 lb. Find a 90% confidence interval for the population mean weight of all such turtles.
A sample of 10 high school students completed a course designed to increase SAT verbal scores. The following is the summary for this group's SAT verbal scores after completion of the course: Σx= 5846, Σx2 =3428148. a. What is the mean and standard deviation for this groups' SAT verbal score? b. What is the 95% confiden
1) Using the data of problem 1.62 page 62 of your textbook, test whether the mean voltage reading at the new location is less than the one at the old location. Note: Make sure to state the assumptions Refer To the Harris Corporation/University of Florida study to determine whether a manufacturing process performed at a remo
How would I find the population proportion for this example? The Fox TV network is considering replacing one of its prime-time crime investigation shows with a new family-oriented comedy show. Before a final decision is made, network executives commission a sample of 400 viewers. After viewing the comedy, 250 indicated they w
If 45 officials in student services earned an average of x(with a line over it) = $50,340 each year: a. Assume that the standard deviation is 16,920 fro salaries of officials . Find the 90% confidence interval for the population mean salary of such personal. What is the margin of error. b. If SD is 10,780, Find the 90% conf
Computing from a large sample, one finds the 95% confidence interval for μ to be (6.8, 14.2). Based on this information alone, determine the 90% confidence interval for μ.
The time it takes for a taxi to drive from the office to the airport was recorded on 40 occasions. It was found that minutes and s = 5 minutes. Give (a) An estimate of μ = population mean time to drive. (b) An approximate 95.4% error margin. Finding Population Mean Estimate Finding 95.4% Margin of Error
1. Consider an infinite population with a normal shape and a mean of 250 and standard deviation of 30. a. Compute the z-scores for the following values of X and locate each on the graph. X Z-score 200 320 220 270 250 b. According to the Empirical rule what percent of the data should be between 220 and 280? Bet
Question: There are 300 welders employed at the Maine Shipyards Corporation. A sample of 30 welders revealed that 18 graduated from a registered welding course. Construct the 95 percent confidence interval for the proportion of all welders who graduated from a registered welding course.
The Star Tribune, a Min.-St. Paul newspaper sponsored a poll designed to reveal opinions about the "photocop" which consist of cameras positioned to catch drivers who run red lights. The cameras photograph the license plates of cars passing through red lights, and those car owners are later mailed traffic violations. The newspap
Question: Towers Perrin, a New York human resources consulting firm, conducted a survey of 1100 employees at medium sized and large companies to determine how dissatisfied employees were with their jobs (The Wall Street Journal, January 29, 2003). A total of 473 employees indicated they strongly disliked their current work ex
Question : Complaints about rising prescription drug prices caused the U.S. Congress to consider laws that would force pharmaceutical companies to offer prescription discounts to senior citizens without drug benefits. The House Government Reform Committee provided data on the prescription cost for some of the most widely used d
Question: The undergraduate grade point average (GPA) for students admitted to the top graduate business schools was 3.37 (Best Graduate Schools, U.S. News and World Report, 2001). Assume this estimate was based on a sample of 120 students admitted to the top schools. Using past years' data, the population standard deviation
Part 1: A study was conducted to see if more than 60% of the American corporate work force felt that they were overdue for a promotion. A random sample of 1500 Americans currently working in a corporate atmosphere was taken. 855 said that they did feel that a promotion was overdue. A 95% confidence interval for estimating t
When would I want a small confidence interval and when would I be satisfied with a larger one? When is a larger sample important?