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    Confidence Interval

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    Confidence interval for mean...

    A previous analysis of paper boxes showed that the the standard deviation of their lengths is 9 millimeters. A packer wishes to find the 99% confidence interval for the average length of a box. How many boxes does he need to measure to be accurate within 2 millimeters?

    Confidence interval - Malfunctioning Equipment

    You decide to measure the time between equipment malfunctions over a one-year period. Over that time you measured 40 electronic products. You made 850 observations with a mean time between equipment failures of 550.35 hours, and a sample standard deviation of 207 hours. Your company supplies the electronic product to anoth

    Confidence interval for average height of US Navy recruits

    A US Navy recruiting center knows from past experience that the height of its recruits are normally distributed with mean 68 inches. The recruiting center wants to test the claim that the average height of this year's recruits is greater than 68 inches. To do this, recruiting personnel take a random sample of 64 recruits from th

    Description of Confidence Intervals

    Consider the given set of average annual household income levels of citizens of selected U.S. metropolitan areas in the attached file. a. Use Excel to obtain a simple sample of size 15 from this frame. b. Using the sample generated in part a, construct a 99% confidence interval for the mean average annual household income

    Statistics - Margin of Error

    See the attached file. 1. Under the case that population standard deviation delta is known and sample size n > 30. Show the margin of error for a 95% confidence interval (CI) for population mean µ as follows c = 1:96 (delta/sqrt n) (c= 1.96 x populations standard mean/square root of sample size n) What will happen

    Statistics

    Sample of 20 pages was taken out replacement from the 1,591 page directory. On each page the main areas devoted to display ads was measured. The data is square millimeters are shown 0 260 356 403 536 0 268 369 428 536 268 396 469 536 162 238 403 536 536 130 a) Construct a 95 per cent confidence intervals for the true mea

    Hypothesis Test: Example Problem

    A survey of an urban university (population 25,450) showed that 870 of 1100 students sampled supported a fee increase to fund improvements to the student recreation center. Using the 95% level of confidence, what is the confidence interval for the true proportion who support the fee increase?

    Statistics - Confidence Interval for μ

    Find a confidence interval for μ assuming that each sample is from a normal population. a. ¯x = 14, σ = 4, n = 5, 90 percent confidence b. ¯x = 37, σ = 5, n = 15, 99 percent confidence c. ¯x = 121, σ = 15, n = 25, 95 percent confidence

    Confidence interval for average annual for retail sales

    Assume the population standard deviation is 3.8 thousand dollars. 4.4 6.5 4.2 8.9 8.7 8.1 6.1 6.0 2.6 2.9 8.1 -1.9 11.9 8.2 6.4 4.7 5.5 4.8 3.0 4.3 -6.0 1.5 2.9 4.8 -1.7 9.4 5.5 5.8 4.7 6.2 15.0 4.1 3.7 5.1 4.2 a) Verify that for the data, x(x bar)=5.1, find 8

    Confidence Interval for standard hemoglobin readings

    The standard hemoglobin reading for healthy adult men is 15g/100ml with a standard deviation of 2g. For a group of 25 men we find a mean hemoglobin of 16.0g. Obtain a 95% confidence interval and give its interpretation.

    Confidence interval of average study time

    Babsie is a public affairs specialist at Park University. A press release issued by Babsie based on some research claims that Park University students study at least as much as the national average for students at four year universities. Across the nation, 73 percent of all students at four year universities study at least four

    Confidence Interval - In 1992, the FAA conducted 86,991 pre-employment drug tests on job applicants who were to be engaged in safety and security-related jobs, and found that 1,143 were positive. ...

    In 1992, the FAA conducted 86,991 pre-employment drug tests on job applicants who were to be engaged in safety and security-related jobs, and found that 1,143 were positive. (a) Construct a 95 percent confidence interval for the population proportion of positive drug tests. (b) Why is the normality assumption not a problem

    Confidence Interval and Hypothesis Testing - 2. A sample of 81 observations is taken from a normal population. The sample mean is 40, and the sample standard deviation of 5. Determine the 95 percent confidence interval for the population mean. 3. Merrill Lynch Securities and Health Care Retirement, Inc, are two large employers in down ... [See the attached Quesstions File]

    2. A sample of 81 observations is taken from a normal population. The sample mean is 40, and the sample standard deviation of 5. Determine the 95 percent confidence interval for the population mean. 3. Merrill Lynch Securities and Health Care Retirement, Inc, are two large employers in down Toledo, OH. They are considering joi

    Level and Width of Confidence Interval of Mean

    Directions: 1) Calculate a point estimate and a 95% confidence interval of the mean. Assuming your data set is normally distributed, determine an appropriate sample size if the maximum allowable error is three units for the attached data set. (Please note: the three units are measure in the unit of measurement of the attache

    95% Confidence interval for mail ad preferences

    A survey showed that out of 200 adults 51% of adults prefer to receive advertisement through the mail. Construct a 95 % confidence interval for the proportion of adults who prefer to receive ads through the mail.

    The Difference Between the Obama and McCain Voting Percentage

    In a new poll where people were asked on whether or not they will vote for a presidential candidate: 1600 people were picked randomly from a population that amounts to about 80 million eligible voters. The results were as follow: N Obama Mccain Undecided 1600 900 600 100 Estim

    Population Means and Confidence Intervals

    1.What sample size would be needed to estimate he population mean to within one-half standard deviation with 95% confidence? 2.A 95% confidence interval estimate for a population mean was computed to be (44.8 to 50.2). Determine the mean of the sample, which was used to determine the interval estimate.

    (1) Biting an unpopped kernel of popcorn hurts! As an experiment, a self-confessed biting an unpopped kernel of popcorn hurts! As an experiment, a self-confessed connoisseur of cheap popcorn carefully counted 773 kernels ... (2) A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech Pages Plus Yellow Pages. On each page, the mean area [See the Attached Questions File.]

    (1) Biting an unpopped kernel of popcorn hurts! As an experiment, a self-confessed biting an unpopped kernel of popcorn hurts! As an experiment, a self-confessed connoisseur of cheap popcorn carefully counted 773 kernels ... (2) A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech

    Daily Gasoline Consumption of a Fleet of 500 Taxis

    The daily gasoline consumption of a fleet of 500 taxis is known to be normally distributed. One, day a sample of 20 taxis is taken, and their mean gasoline consumption is found to have been 20.8 gallons, with a standard deviation of 3.7 gallons. Construct a 95 percent confidence interval for the day's mean gasoline consumption

    Chebyshev Theorem and Confidence Interval

    1. a) Use Chebyshev's theorem to find what percent of the values will fall between 120 and 150 for a data set with mean of 135 and standard deviation of 7.5 b) Use the Empirical Rule to find what two values 95% of the data will fall between for a data set with mean 234 and standard deviation of 12 2. An aptitude test ha

    2. The following table classifies 800 telephone calls by type (local or long distance) and by length: (6 points) a. What is the probability that a call sampled at random out of this population is local and 1 -5 minutes long? b. What is the probability that a call sampled at random is long distance? c. What is the probability that a call is not 5+ minutes given that is a long distance call?

    Please answer the following questions in Microsoft Excel. There are six questions total. Work on how to do it should be shown. 2. The following table classifies 800 telephone calls by type (local or long distance) and by length: (6 points) a. What is the probability that a call sampled at random out of this population is l

    Confidence Intervals - Lunches

    In a certain countrywide school district, a survey of 350 students showed that 28% carried their lunches to school. Find the 95% confidence interval of the true proportion of students who carried their lunches to school. If the cafeteria manager wanted to be reasonably sure that all the children who didn't bring their lunches co

    Confidence Intervals and Sample Size Determination

    A recent study indicated that 29% of the 100 women over age 55 in the study were widows. a. How large a sample must one take to be 90% confident that the estimate is within 0.05 of the true proportion of women over ages 55 who are widows? b. If no estimate of the sample proportion is available how large should the sample

    Statistics - Find the Confidence Interval

    How do you find the Confidence Interval for a particular Confidence Level, such as 95%, for a sample of more than 30 people? Show the exact formulas that you use in this situation to calculate the sample standard deviation and standard error?

    Confidence Interval - Sample of VCR Owners

    NBC asked a sample of VCR owners to record "Late Night with David Letterman" on their VCRs. Of the 125 VCR owners surveyed, 83 either "gave up or screwed up" because they did not understand how to program the VCR. (a) Construct a 90 percent confidence interval for the true proportion of VCR owners who cannot program their VCRs.

    90% Confidence Interval on the Stock Exchange

    Joel Friedlander is a broker on the New York Stock exchange who is curious about the amount of time between the placement and the execution of a market order. Joel sampled 25 orders and found that the mean time to execution was 24.3 minutes with a standard deviation of 3.2 minutes. Help Joel by constructing a 90 percent confid

    Computing Confidence Interval for Mean

    Suppose a sample of 50 is taken from a population with a standard deviation of 27 and that the sample mean is 86. Establish a 95.5% interval estimate for the population mean. Suppose, instead, that the sample size was 5000. Establish a 95.5% interval estimate for the population mean. Why might you prefer one estimate over the