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    Confidence Interval

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    Dental Plan as part of the Benefits Package; one family Per yer, Sample of 45

    The Human Relations Department of Electronics, Inc., would like to include a dental plan as part of the benefits package. The question is: How much does a typical employee and his or her family spend per year on dental expenses? A sample of 45 employees reveals the mean amount spent last year was $1,820, with a standard deviatio

    Construct a 90% confidence interval for the population standard deviation

    The grade point averages for 10 randomly selected students are listed in column 1 of the minitab worksheet. the distribution of GPAs is known to be approximately normally distributed. If possible, construct a 90% confidence interval for the population standard deviation. Interpret the meaning of the interval. GPAs 2.0

    Gun Control Confidence Interval

    Many people think that the national lobby's successful fight against gun control legislation is reflecting the will of a minority in Americans. A random sample of 40 citizens yielded 22 who are in favor of gun control legislation. If possible, estimate the true proportion of all Americans who are in favor of gun control legis

    Constructing Confidence Intervals - FDA

    To help customers assess the risks they are taking, the FDA publishes the amount of nicotine found in all commerical brands of cigarettes. A new cigarette has recently been marketed. The FDA tests on this cigarette gave a mean nicotine content of 24.2 milligrams and standard deviation of 2.7 milligrams for a sample of n=9 cigare

    Construct a 99% confidence interval for the proportion

    A survey of 600 non-fatal accidents showed that 278 involved the use of a cell phone. If possible, construct a 99% confidence interval for the proportion of non-fatal accidents that involved the use of a cell phone. Interpret the meaning of this interrval.

    Construct a 98% Confidence Interval

    The mean life time of a random sample of 12 microwave ovens is 8.6 years with a standard deviation of 2.7 years. If possible, construct the 98% confidence interval for the population standard deviation. The distribution of life time of microwave ovens is known to be skewed left.

    Finding Appropriate Sample Mean

    In order to set rates, an insurance company is trying to estimate the number of sick days that full time workers at an auto repair shop take per year. A previous study indicated that the population standard deviation was 2.1 days. How do I find a sample large enough for the company that wants to be 92% confident that the true

    Construct a 97% Confidence Interval

    In a recent study of 51 eighth graders, the mean number of hours per week that they watched television 21.9. assume the standard deviation =5.8 hours. If possible, find the 97% confidence interval of the mean. Interpret the meaning of this interval. If the standard deviation is doubled to 11.6, what will be the effect on

    Confidence Intervals - Proportion

    A manufacturer of golf equipment wishes to estimate the number of left-handed golfers. How large of a sample is needed in order to be 95% confident that the sample proportion will not differ from the true proportion by more than 3%? A previous study indicates that the proportion of left-handed golfers is 11%. How large of

    Determining and Adjusting Sample Size

    1. Your professional organization wants to survey graduates in your field. It wishes to take a random sample to estimate the proportion of graduates who feel they got an "excellent education" during their college study days. The executive director of the association has indicated the it would be desirable for 90% confidence int

    Calculation of Confidence Interval

    Please see attached file for full problem description. The breaking strengths of cables produced by a certain manufacturer have a standard deviation of pounds. A random sample of newly manufactured cables has a mean breaking strength of pounds. Based on this sample, find a confidence interval for the true mean breaking st

    Step by step method for construction of confidence interval is discussed here.

    Probability 1. According to Investment Digest ("Diversification and the Risk/Reward Relationship", Winter 1994, 1-3), the mean of the annual return for common stocks from 1926 to 1992 was 14.4%, and the standard deviation of the annual return was 20.5%. During the same 67-year time span, the mean of the annual return for long

    Statistics Problem: Finding a Significant Difference

    The manufacture of the X-15 steel belted radial truck tire claims that the mean mileage the tire can be driven before the tread wears out is 60,000 miles. The standard deviation of the mileage is 5,000 miles. The Crosset Truck Company bought 48 tires and found that the mean mileage for their truck is 59,500 miles. Is Crossets ex

    Confidence interval

    The standard deviation of test scores on a certain achievement test is 10.8 . A random sample of 80 scores on this test had a mean of 75.4 . Based on this sample, find a 90% confidence interval for the true mean of all scores. Then complete the table below. Carry your intermediate computations to at least three decimal places.

    Confidence Interval, Sample Size and Type I Error

    1. If the level of confidence is decreased from 95 percent to 90 percent, but the allowable error and the standard deviation remain the same, the required sample size for determining the confidence interval will be: a. increased. b. decreased. c. unchanged. 2. The probability of committing a type

    Confidence intervals and cancer potency

    Please see attachment. 7. Using the upper 95% confidence level for the 20 mg/kg-day dose, calculate the cancer potency by drawing a straight line from the 20 mg/kg-day dose level to the origin. 8. Do the same using the lower 95% confidence level. 9. Calculate the range of doses that would correspond to a one in a millio

    Confidence levels and relevant probabilities

    Hypothetical Data for Kil-EZ Carcinogenicity Test Number of test rats Number of rats with tumors Rat test dose in mg Kil-EZ per kg rat body weight (mg/kg/day) Probability of a rat's developing tumors Lower 95% confidence level Upper 95% confidence level 50 1 0 .02 50 5 20 .10 50 10 40 .20 50 20 80 .40 50 7* 160 .

    Sample size and confidence interval calculation

    Consumer products companies design different promotional activities to accomplish different goals. According to a spokesperson for General Mills, the company's cents-off coupon offers are designed to convince people to buy its products, while its refund offers (money returned with proof of repeated purchases) are designed to en

    The importance of point estimates & confidence intervals

    In our real world, where the quality and quantity of information ranges from excellent to terrible, would some measure of the certainty of the data tend to lead to better decisions? Can point estimates and confidence intervals help to provide some measure as to the certainty of data values?

    Finding the Margin of Error and Confidence Level

    I need to find out how to calculate the margin of error when given the data: c=95; s=0.10; n=20; x(bar) = 1.5 and how to construct a confidence interval of the population mean. This example is similar to my studies.

    Estimating Population Values and confidence interval

    The corporate operations manager for the Phillips Oil Company has his staff working on a new service-station layout plan that would potentially alter the ratio of regular unleaded pumps to other gasoline pumps (premium, super premium, etc) that are placed at a station. As part of the staff's analysis, they are interested in

    Estimating Population Values

    The AIMS Investment Company is interested in estimating the average number of mutual funds its customers have in their portfolios. a. based on the sample data, construct a 90% confidence interval estimate for the mean number of mutual funds for all their customers. Interpret this interval. b. Suppose that the interval est

    Estimating Population Values

    7.14 The First National bank is considering a survey of its customers to estimate the man number of checks written per month. A sample of 360 customers was selected. The sample values were _ X = 33.4 S = 11.2 a. Provide a 90% confidence interval e

    Confidence Interval Calculations

    Assume you are a tire manufacturer and want to determine what the tread life of a new line of tires is. A sample of 100 tires are run to failure and the average mileage is computed to be 55,000 miles with a standard deviation of 1000 miles. Compute the 95% confidence interval on the population mean. Interpret the interval. W