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Confidence Interval

Point Estimation and Interval estimation

47) Arthur D. Little, Inc. estimates that approximately 70% of mail received by a household is advertisements (Time, July 14, 1997). A sample of 20 households shows the following data for the number of advertisements received and the total number of pieces of mail received during one week. a) What is the point estimate of the

Department store chain, confidence interval for mean

1. A major department store chain is interested in estimating the average amount its credit card customers spent on their first visit to the chain's new store in the mall. Fifteen credit card accounts were randomly sampled and analyzed with the following results: Χ = $50.50 and s2 = 400. Assuming the distribution of th

To find the confidence interval of difference of mean

Construct a 90% confidence interval for mu sub d, the mean of the differences d for the population of paired data. Assume that the population of paired differences is normally distributed. d-bar = 3.125; s d = 2.911; n = 8 2.435 < <MUµd < 3.815 1.175 < µd < 5.075 2.435 < µd < 5.075

Confidence interval and testing of hypothesis problems

1. A manufacturer of small appliances employs a market research firm to estimate retail sales of its products by gathering information from a sample of retail stores. This month an SRS of 75 stores in the Midwest sales region finds that these stores sold an average of 24 of the manufacturer's hand mixers, with standard deviatio

Confidence level - margin of error

Use the confidence level and sample data to find the margin of error E. Weights of eggs: 95% confidence; n = 49, x-bar = 1.70 oz, sigma = 0.33 oz

Confidence interval for a population mean

A researcher wishes to construct a 95% confidence interval for a population mean. She selects a simple random sample of size n=20 from the population. The population is normally distributed and sigma is unknown. When constructing the confidence interval, the researcher should use the t distribution; however, she incorrectly uses

Confidence level and sample data

Use the confidence level and sample data to find a confidence interval for estimating the population mean m. Test scores: n = 101, x-bar = 96.8, sigma = 8.3, 99 percent confidence

Probability and Statistics

1. TFQ: Amy wants to find a 96% confidence interval for the amount of time it takes to get to work. She kept records for 35 days and found her average time to commute to work was 20.5 minutes with a standard deviation of 3.6 minutes. Amy's maximum error of estimate would be 1.25 minutes. 2. TFQ: Charles wants to be 90% c


Question 1: Find the number of successes x suggested by the given statement. Among 680 adults selected randomly from among the residents of one town, 27.2% said that they favor stronger gun-control laws. a. 183 b. 184 c. 186 d. 185 Solve the problem. In a game, you have a 1/29 probabilit

Construction of confidence interval for mean and population proportion.

* Construct the indicated confidence interval for the difference between population proportions p1 - p2. Assume that the samples are independent and that they have been randomly selected. x1 = 57, n1 = 95 and x2 = 84, n2 = 96; Construct a 98% confidence interval for the difference between population proportions p1 - p2. ....

Estimation: Confidence Intervals and Sample Size

1) In a poll to estimate presidential popularity, each person in a random sample of 1,000 voters was asked to agree with one of the following statements: 1. The President is doing a good job. 2. The President is doing a poor job. 3. I have no opinion. A total of 560 respondents selected the first statement, indicating

Hypothesis Testing, Confidence Intervals and ANOVA

1) The following is sample information. Test the hypothesis that the treatment mean are equal. Use the .05 significance level. Treatment 1 Treatment 2 Treatment 3 8 3 3 11 2 4 10 1 5 3 4 2 T1= 29 T2= 11 T3= 16 TOTAL T=56 N1= 3 N=5 N=4 N=12 9.6 (MEAN) 2.2 (MEAN) 4 (MEAN) 15.8 FOR GRAND MEAN A. State the

To find 99% confidence interval of mean difference in temperatures

The table gives the average low tempatures in January and July for twelve cities. Construct a 99% confidence interval for the mean temperature difference (January-July) between winter and summer. Assume the population are normally distributed. Cities JANUARY JULY Chhose the 99% confidence interval for the mean diffe

Law of Large Numbers

In regards to the stock market returns, what is the significance of the Law of Large Numbers? What do confidence intervals represent? What are the differences between z-statistics and t-statistics?

Confidence Interval and Probability Questions

1. Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS e-mail for non-business communications. A random sample of 200 e-mail messages was selected. Thirty of the messages were not business related. The 95% confidence interval for the population proportion is _________. a.0.091 to 0.209 b. 0.108 to 0.192

Determining a 99% Confidence Interval

a) A seed distributor guarantees 95% germination of the seeds he supplies. A retailer has an agreement with the distributor, under which he may test a random sample of 200 seeds for germination and send the whole batch back to the manufacturer if the proportion of germinating seeds is significantly below 95%. With a significance

Statistical Processes for Hypothesis Testing

(See attached file for full problem description with proper equations) An engineer was interested in comparing the variability of the power of a laser at current levels of 16 amps (X) and 20 amps (Y). To do so, random samples of 25 observations of power readings were obtained at each current level. The samples were taken hi

Application of Confidence Intervals

1. You are the manager of a tax preparation center. A vendor brings in a new software package that he says can reduce the amount of time spent preparing taxes. What would your null hypothesis be? With your null who is bearing the risk of Type I and Type II errors? 2. What is the value of establishing confidence intervals

Statistical processes

2. A company manufactures steel bolts that continuously feed an assembly line downstream. Historically, the thickness of these bolts follows a normal distribution with a standard deviation of 1.6 mm. A recent random sample of 10 observations yielded these values of thickness, in mm: 9.7 9.9 10.3 10.1 10.5 9.4 9.9 10.1

Hypothesis testing and confidence interval

Refer to the sample results below for the measured nicotine contents of randomly selected filtered and non-filtered king-size cigarettes. All measurements are in milligrams. a. use a 0.05 significance level to test the claim that king-size cigarettes with filters have a lower mean amount of nicotine than the mean amount of nic


Smith Travel Research provides information on the one-night cost of hotel rooms throughout the United States (USA today, July 8, 2002). Use $2 as the desired margin of error and $22.50 as the planning value of the population standard deviation to find the sample size recommended in (a), (b), and (c). a. Determine a 90% confid

Calculate a 99 percent confidence interval for μ

The weight of a product is measured in pounds. A sample of 50 units is taken from a batch. The sample yielded the following results: = 75 lbs., and s = 10 lbs. Calculate a 99 percent confidence interval for μ.

Solutions to Various Statistics Problems

1. Each day of the year a large sample of cellular phone calls is selected and a 95% confidence interval is calculated for the mean length of all cellular phone calls on that day. Of these 365 confidence intervals, one for each day of the year, approximately how many will cover their respective population means? Explain your rea

Upper Bounds, One Sided Confidence Interval: Online Fashion Store

An internal control policy for an online fashion accessories store requires a quality assurance check before a shipment is made. The tolerable exception rate for this internal control is 0.05. During an audit, 500 shipping records were sampled from a population of 5,000 shipping records and 12 were found that violated the cont

Confidence Intervals & Tails

What do we mean by confidence intervals? What do the 'tails' of a distribution signify? Provide an example of a one tailed problem.

Confidence Interval & Probable Value

Confidence intervals are frequently used to assess a population and determine the probable value for a population parameter. I need an application or example pertaining to Customs & immigration and the farming business. Please describe your examples.

Probability in Business Decision Making

1. What is the role of probability concepts in business decision making? 2. Define probability concepts. 3. Give two examples that are related to the farming Industry or any other Industry or professional environment. THANK YOU, your help is greatly appreciated.

Comparing Population Means

Comparing Two Population Means Instructor Reputation and Teacher Ratings (revisited) How powerful are rumors? Frequently, students ask friends and/or look at instructor evaluations to decide if a class is worth taking. Kelley (1950) found that instructor reputation has a profound impact on actual teaching ratings. Towler a

Notes on Scattergrams, hypothesis, confidence interval

(See attached file for full problem description) --- 1.7 Based on the data for the years 1962 to 1977 for the United States, Dale Bails and Larry Peppers17 obtained the following demand function for automobiles: Yt = 5807 + 3.24Xt r2 = 0.22 Se = (1.634) Where Y = retail sales of passenger cars (thou