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Confidence Interval

Confidence interval estimation.

In a certain region of the country, average radar echo duration of lightning flashes is .81 sec and a standard deviation of .34 sec. Note, that these are population values. Calculate a 99% (two sided) confidence interval for the true average echo duration ? , for a random sample of 100 lightening flashes

Sample Size and Probability

1 ) Management has asked a lab to produce accurate results at the 88% level for a first time experiment. the management wants the final error to be within 1/10th of the sample standard deviation. Find the sample size. 2) A sample of 16 women had a mean score of 275 and a variance value of 360. A. find both the 955 and 99

T-distribution or CLT: Two sided interval analysis on test score

Assume a very large normally distributed population of scores on a test with mean 77 and standard deviation 7. a. Find the two sided interval that includes 90% of this population b. Suppose a sample of 40 members is randomly selected from this population. Find an interval (two sided) that provides a 5% error in the estimat

ElecMart: Two sided confidence intervals fo customers' orders

See attached data file. Problem (P_Data on the template) contains data for 400 customers. This company, ElecMart sells electronic appliances for mail-in orders. Consider this data as a random sample from all of ElecMart mail-in orders. Find the following two sided confidence intervals: a. Find the 95% Confidence Inter

Control Limits (Confidence Intervals)

11. Product filling weights for a cereal manufacturer are normally distributed with a mean of 350 grams, a variance of 225 grams and a standard deviation of 15 grams. a) Develop the control limits that would be used on the company's x-bar control charts of samples of sizes 10, 20, 30. b) What happens to the control limits a

Confidence Interval: Difference in Proportion

Borst et.al. investigated the relation of ego development, age, gender, and diagnosis to suicidality among adolescent psychiatric inpatients. Their sample consisted of 96 boys and 123 girls between the ages of 12 and 16 years selected from admissions to a child and adolescent unit of a private psychiatric hospital. Suicide attem

Two Populations confidence intervals for Maxforce, Inc.

Maxforce, Inc., manufactures racquetball racquets by two different manufacturing processes (A and B). Because the management of this company is interested in estimating the difference between the average time it takes each process to produce a racquet, they select independent samples from each process. The results of the samples

Confidence Intervals of Two Populations

The following sample information is given concerning the ACT scores of high school seniors form two local schools. School A School B n1 = 14 n2= 15 x1 = 25 x2 = 23 var1 = 16 var 2 = 10 Develop a 95% confidence interval estimate for the difference between the two populations.

Statistics: Confidence intervals explanation

What do confidence intervals represent? What is the most controllable method of increasing the precision of or narrowing the confidence interval? What percentage of times will the mean, or population proportion, not be found within the confidence interval? about 200 words, no references

Case Problem with data Set.

Please see the attached problem with data set. Full view in book found here: http://books.google.com/books?id=_sOSAXTuy8cC&lpg=PA330&ots=24jaKDiokN&dq=case%20problem%202%20gulf%20real%20estate%20properties&pg=PA330#v=onepage&q=case%20problem%202%20gulf%20real%20estate%20properties&f=false See the description here. It

Confidence Interval for Proportion

On January 7, 2000, the Gallup Organization released the results of a poll comparing the lifestyles of today with previous times. The survey results were based on telephone interviews with a randomly selected national sample of 1,031 adults, 19 years and older. a. Gallup found that 42 percent of the respondents said that they

Decision Analysis in EXCEL

Please see attached files for further information. 1. A toy company has developed a new toy for the upcoming Christmas season. Since this toy is considerably different from the ones it has manufactured previously, the company will need to develop a new production facility for it. Three facility sizes-small, medium, and large-

P-Value - Null Hypothesis - Productivity Data for plant worker productivity

See attached file. 11.51. A plant manager has collected productivity data for a sample of workers, intending to see whether there is a difference in the number of units they produce on Monday versus Thursday. The results (units produced) are in data file XR11051. Using the 0.01 level of significance, evaluate the null hypothe

Confidence Interval & Prediction Interval

The data from exercise 1 follow. xi 1 2 3 4 5 yi 3 7 5 11 14 a. Use equation (14.23) to estimate the standard deviation of yp when x = 4. (Formula is given in the attachment). b. Use equation (14.24) to develop a 95% confidence interval estimate of the expected

Calculation of Confidence Interval using T-Distribution

1. A recent study of 50 self-service gasoline stations in the Greater Cincinnati' Northern Kentucky metropolitan area revealed that the mean price of unleaded gas was $2.029 per gallon. The sample standard deviation was $0.03 per gallon. Determine a 99 percent confidence interval for the population mean price. 2. The Bad

Confidence Interval for Proportion: Defective dolls

A shipment of 500 dolls is received by Panda Importers. The quality control manager selects a random sample of 75 to test. Five are bound to be defective. Construct a 90 percent confidence interval for the population proportion of defective dolls in the shipment. Ans should be 0.06666 + / - 1.645 sqrt (0.667 (1-0.667 / 75

Mean weekly child care cost for employees

Merrill Lynch Securities and Health Care Retirement, Inc., are two large employers in downtown Toledo, Ohio. They are considering jointly offering child care for their employees. As apart of the feasibility study, they wish to estimate the mean weekly child-care cost of their employees. A sample of 10 employees who use child car

Confidence Interval, Interval Estimates, Finite Population

SEE ATTACHED FILE - Sample Size, Finite Population (9.110) NOTE: Please use an Excel spreadsheet for response. Please do not just provide the answer but show in complete detail how you arrived at the answer, step-by-step, from the beginning to the end of the solution.

Misspelled words

Dr. Patton is a professor of English. Recently she counted the number of misspelled words in a group of student essays. She noted the distribution of misspelled words per essay followed the normal distribution with a standard deviation of 2.44 words per essay. For her 10 A.M. section of 40 students, the mean number of misspe

Confidence interval for µ based on raw data and ? known for paint samples

See the attached Excel spreadsheet and 2 files which may be of assistance in determining the Mean. The spreadsheet contains the amount of fluid ounces of each of the 40 paint cans. NOTE: Please use an Excel spreadsheet for response. Please do not just provide the answers but show in complete detail how you arrived at the ans

Confidence Interval Estimates for Means

A simple random sample of 25 has been collected from a normally distributed population for which it is known that ? = 17.0. The sample mean has been calculated as 342.0, and the sample standard deviation is s = 14.9. Construct and interpret the 95% and 99% confidence intervals for the population mean. NOTE: Please use a

Hypothesis Testing & Confidence Interval: Mean sleep

See data file attached. Compare the mean of the "Sleep" data to the national average of 6.9, with a standard deviation of 1.38. Perform the following statistical operations using a Microsoft Word document: State a research (directional) hypothesis and the null hypothesis about the populations Determine the cutoff sampl

Confidence Interval Problem: Delivery Truck Manager Example

A delivery truck manager takes a sample of 25 delivery trucks and calculates the sample mean and deviation for the cost of operation. A 95% confidence interval for the mean cost is constructed and found to be $253 to $320. He reasons that this interval contains the mean operating cost for the fleet of delivery trucks since the s

Statistics Part III for Managers: 4 problems

1. If you want to be 95% confident of estimating the population portion to within a sampling error of + 0.02 and there is historical evidence that the population proportion is approximately 0.40, what sample size is needed? 2. In a study of 500 executives, 315 stated that their company informally monitored social

Statistics for Managers: Confidence interval estimate problems

1. If X=85 (sample mean), 8 is population standard deviation, and n=64 is sample size, construct a confidence interval estimate for the population mean. 2. The manager of a paint supply store wants to estimate the actual amount of paint contained in 1-gallon cans purchased from a nationally known manufacturer. The manufactue

Effect of extreme value on confidence interval

Compute a 95% confidence interval for the population mean, based on the sample 25, 27, 23, 24, 25, 24 and 59. Change the number from 59 to 24 and recalculate the confidence interval. Using the results, describe the effect of an outlier or extreme value on the confidence interval.