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Confidence Interval

Random Sampling in EXCEL and Confidence Interval Estimate

The employee benefits manager of a small private university would like to estimate the proportion of full-time employees who prefer adopting the first (i.e., plan A) of three available health care plans in the coming annual enrollment period. A reliable frame of the university's employees and their tentative preferences are in t

Confidence interval for average value for prescriptions

The BelSante Company operates retail pharmacies in 10 Eastern states. Recently, the company's internal audit department selected a random sample of 300 prescriptions issued throughout the system. The objective of the sampling was to estimate the average dollar value of all prescriptions issued by the company. The following data


Probability In Excel 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 19.4%, and the standard deviation of the annual return was 24.5%. During the same 67-year time span, the mean of the annual r

Statistics: Confidence intervals for sample; Cohen's guidelines, two-tailed test

8.22. Calculate the 95% confidence interval for the following fictional data regarding daily TV viewing habits: µ = 4.7; σ = 1.3 hours; sample of 78 people with a mean of 4.1 hours. 8.30. For each of the following d values, identify the size of the effect using Cohen's guidelines. (a) d = 0.79 (b) d = - 0.43 (c) d = 0

Compute confidence intervals for data given.

Compute the confidence interval(s) of your data On a 29 count, for education, the mean is 12.62069,the mode is 12, as well as the median. For experience the mean is 24.51724138, the mode is 33, and the median is 22. Wages mean is 30383.06897, the median is 28168, and there was no mode found. For wages the range was 72604, varian

Statistics symbols, confidence intervals, z test

8.16. In statistics, concepts are often expressed in symbols and equations. For each of the following, (i) identify the incorrect symbol, (ii) state what the correct symbol should be, and (iii) explain why the initial symbol was incorrect: (a) Мlower =-z(σ) + Msample The incorrect symbol is σ. It should be σm because i

Calculations for Hypothesis Testing and Confidence Intervals

Please see the attached problem. A manufacturing company produces water filters for home refrigerators. The process has typically produced about 4% defective. A recently designed experiment has led to changing the seal to reduce defects. With the process running using the new seal, a random sample of 300 filters yielded 7 def

Statistics: Yaschchin discusses process for chemical etching of silicon wafers

Please see the attached problem. 2. Yaschchin (1995) discusses a process for the chemical etching of silicon wafers used in itegrated circuits. This company wishes to detect an increase in the thickness of the silicon oxide layers because thicker layers require longer etching times. Process specifications state a target valu

Statistics 4.10: Kane discusses concentricity of engine oil seal groove

See the attached problem. 4.10. Kane (1986) discusses the concentricity of an engine oil seal groove. Historically, the standard deviation for the concentricity is 0.7. The target average concentricity is 5.6. To monitor this process, he periodically takes a random sample of three measurements. a. A recent sample yielded

Statistics: estimate the proportion of the population

Part I. Suppose the coach of the football team wants to estimate the proportion of the population of fans who support his current starter lineup. The coach wants the estimate to be .04 of the true proportion. Assume a 99 percent level of confidence. The coach estimated the proportion supporting the current starter lineup to

Constructing 95 percent confidence intervals

A reporter took a simple random sample of 725 voters in a region that has a population of 12,457. He recorded that 338 of the persons polled favored Issue 1 on the ballot. Construct a 95% confidence interval for the proportion that favor the issue and then discuss what the reporter can and cannot say in his report. If you were t


1. Consider a normal population with a mean+ 25 and a standard deviation= 7.0. A. Calculate the standard score for a value x of 24. B. Calculate the standard score for a randomly selected sample of 45 with a sample mean = 25. C. Explain why the standard scores of 24 are different between A and B above. 2. Assume tha

Confidence interval

The office manager for a large company is studying the usage of its copy machines. A random sample of six copy machines revealed the following number of copies (reported in 000s) made yesterday. Please help with attached.

Maximum error of estimate.

1. Consider a population with a mean =73.6 and a standard deviation=5.38 A. Calculate the z-score for sample mean=72.7 from a sample size of 45. B. Could this z-score be used in calculating probabilities using Table 3 in the Appendix B. Why or why not? 2. Given a level of confidence of 99% and a population standard deviatio

Estimate the sample size and population mean

A1) Suppose the U.S. President wants an estimate of the proportion of the population who support his current policy toward revisions in the Social Security system. The president wants the estimate to be within .04 of the true proportion. Assume a 95 percent level of confidence. The president's political advisers estimated the p

4 Statistics problems: Confidence interval estimate of mean

Q-3a. A stationery store wants to estimate the mean retail value of greeting cards purchased by its customers when they visit the store. A random sample of 15 customers indicates a mean amount of $2.55 with a standard deviation of $0.44 per customer per visit. Assuming a normal distribution, construct a 95% confidence inter

Confidence Interval - statistics

A survey of individuals who passed the BAR finds the average starting salary for lawyers to be $75,215 for 36 individuals sampled. If the population standard deviation is $15,990 find a 90% confidence interval for the true mean. Round your answers to the nearest whole number.

Hypothesis testing: wealth

Is there any difference between the proportion of Americans who wish they were rich and the proportion of Canadians who wish they were rich? A random sample of 1000 Americans showed that 550 wish they were rich, while a random sample of 500 Canadians showed that 225 wished they were rich. a. Find a 97.5% confidence interval f