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    Confidence Interval

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    Confidence Interval

    49 items are randomly selected from a population of 500 items. The sample mean is 40, and the sample standard deviation 9. Develop a 99 percent confidence interval for the population mean.

    Confidence interval

    A quality control inspector is concerned with the average amount of weight that can be held by a type of steel beam. A random sample of five beams is tested with the following amounts of weight added (in thousands of pounds): 9, 11,10,10,8 Assuming the population is distributed normal, construct a 95% confidence interval

    3844-Statistical positioning

    Assume that federal regulations require that the average smoke stack concentration of a certain industrial pollutant must not exceed 135 ppm. The EPA suspects one factory is in violation.The EPA randomly collects 31 independent specimens of smoke from the factory smokestack,one for each day in October and performs extensive anal

    Construct the confidence interval

    Construct the confidence interval. Requires either the use of t distribution or the normal distribution. Hospital costs for accident victims who wore seatbelts. 20 randomly selected cases have a distribution that appears to be bell-shaped with a mean of $9004 and a standard deviation of $5629. Construct the 99% confidenc

    Use the degree of confidence and sample data

    Use the degree of confidence and sample data to find a) the margin of error and b) the confidence interval for the population mean u. Assume the population has a normal distribution. Salaries of pilots: 99% confidence; n=12, mean of values in sample = $97,334, s= $17,747

    Construct the 99% confidence interval

    4400 students surveyed about length of time to complete bachelor's. The mean is 5.15 years and the standard deviant is 1.68 years. Based on these sample data, construct the 99% confidence interval for the mean time required by all students.

    Confidence Interval Population Mean

    Details: The estimated value of a population mean is $120, and the upper limit of the 90% confidence interval is $140. A 95% confidence interval has also been constructed. Given this information, which of the following best describes the lower limit of the 95% confidence interval?

    Confidence intervals

    In random, independent samples of 225 adults and 375 teenagers who watched a certain television show... (see attached)

    Confidence intervals

    A random sample of 275 bolts from machine A contained 27 defective bolts... (see attached)

    Statistics - confidence intervals

    The average weekly earnings for women in managerial and professional positions is $685 with a standard deviation of $45. Salaries are normally distributed. Answer the following questions. a. What is the probability that a woman will have a weekly salary of more than $650? b. What is the probability that a woman will hav

    Confidence interval, error of estimate, sample size

    In the publication Employment and Earnings, information on the ages of people in the civilian labor force was published. Seventy-five people in the civilian labor force are randomly selected. The mean age is 37.4 years with a standard deviation of 10.3 years. a. Find the 99% confidence interval for the mean age. b. W

    Use given degree of confidence and sample data

    Use given degree of confidence and sample data to find a) margin of error E and b) the confidence interval for the population mean mu. Starting salaries of college graduates who have taken a statistics course: 95% confidence; n=100, mean of the values in a sample (x with line above)= $43,704, s= $9879.

    Refer to the OECD data, which reports information on census, economic, and business data for 29 countries. a. Develop a 90 percent confidence interval for the mean percent of the population over 65 years. b. Develop a 90 percent confidence interval for the mean energy use.

    Details: Refer to the OECD data, which reports information on census, economic, and business data for 29 countries. a. Develop a 90 percent confidence interval for the mean percent of the population over 65 years. b. Develop a 90 percent confidence interval for the mean energy use.

    Confidence interval

    The NCAA reported that the mean number of hours spent per week on coaching and recruiting by college football assistant coaches during the season is 70. A random sample of 50 assistant coaches showed the sample mean to be 68.6 hours, with a standard deviation of 8.2 hours. a. Using the sample data, construct a 99 percent con

    Find a 90% prediction interval for the individual value

    QUESTION A: Assume that there is a correlation between two variables, X and Y. Based on the information provided below, calculate the correlation coefficient. X 31,30,32,19,25,22,30,19,18,20 Y 32,30,25,22,20,19,18,17,16,15 QUESTION B: Find a 90% prediction interval for the individual value of Y if X

    Confidence interval for a population proportion..

    A researcher wishes to estimate the proportion of X-ray machines that malfunction. A random sample of 275 machines is taken, and 82 of the machines in the sample malfunction. Based upon this, compute a 90% confidence interval for the proportion of all X-ray machines that malfunction. Then complete the table below. Carry your

    What is the lower/upper limit of the 99% confidence interval?

    To estimate the percentage of a species of rodent that carries a specific viral infection, 150 rodents are randomly selected and examined, and 76 of them are found to be infected. Based upon this, find a 99% confidence interval for the proportion of all rodents of this species that are infected with the virus. Then complete the

    Standard deviation, confidence interval

    1. When the level of confidence and sample standard deviation remain the same, a confidence interval for a population mean based on a sample of n=100 will be ______ a confidence interval for a population mean based on a sample of n=50 a) wider than b) Narrower than c) equal to Explain answer: 2). If the box wei

    Confidence intervals for the estimation of population mean

    The mean age of a sample of 60 students from a class was found out to be 25.3 years. The variance in population age was 16 years. (a) Calculate a point estimate for the population mean (b) Find the 95% Confidence interval for the population mean. (c) Find the 99% Confidence interval for the population mean.

    Confidence interval for population variance

    A random sample of size 9 of a random variable X gave a variance of 3.0. Find a 95% confidence interval for the population variance, assuming that X is normally distributed.

    A confidence interval of the mean is determined.

    This problem is solved: Let's summarize the method for finding the 95% confidence interval using a step-by-step illustration. Suppose that a certain automobile company wishes to determine the expected miles per gallon for one of its new models. Based on years of experience with cars, the company statistician realizes that not

    The answer to 99% Confidence Interval

    The standard deviation of the daily demand for a product is an important factor for inventory control for the product. Suppose that a pharmacy wants to estimate the standard deviation of the daily demand for a certain antibiotic. It is known that the daily demand for this antibiotic follows an approximately normal distribution.

    Confidence Interval for a Population with Standard Deviation

    A finance company needs to estimate the mean number of credit cards held by an American family. From past experience, the company knows that the standard deviation of the population is 1.16 cards. The company takes a random sample of n=31 families and finds the sample mean number of cards to be 4.6. Use this data to find a 90% c

    Conference interval

    A consulting firm which does consulting jobs on a cost per job basis wants to estimate its average pay per hour. The firm's manager takes a random sample of n=30 jobs and calculates the pay per an hour. The par per an hour values are listed below, rounded to the nearest dollar. 17 23 14 20 68 40 31 19 19 32 13 37 32 28 34 23 2

    Confidence Interval for true mean

    A savings and loan association needs information concerning the checking account balances of it's local customers. A random sample of 14 accounts was checked, yielding the following balances (rounded to the nearest dollar): 701 379 349 828 499 174 786 762 580 943 741 798 311 1096 Find a 99% confidence interval for the true me

    Compute a 95% confidence interval for the standard deviation of the above data.

    A financial analyst, known for her excellent track record, has decided to part company with her old partners and to enter the venture capital area. In it's publicity brochure, the firm she joins lists the market adjusted rate of return that their new partner achieved during her previous tenure. The table below shows these return