Explore BrainMass

Confidence Interval

Confidence Interva for True Mean Weight of Random Sample

A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighed on a very accurate scale. The results in grams were 3.087 3.131 3.241 3.241 3.270 3.353 3.400 3.411 3.437 3.477 (a) Construct a 90 percent confidence interval for the true mean weight. (b) What sample size would be necessary to estim

Confidence Interval for a poll of people to sample a population

Suppose you conduct a poll if people like some product or like some TV-show. Assign your numbers for total number of people you asked (n - sample size), numbers of people who answered "yes" to the given question (n1), calculate sample proportion p = n1/n and then calculate confidence interval for population proportion. Appl

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

Confidence Interval estimate defined

How do I define the the population and select a simple random sample of size n from the population? A random sample of n=12 values taken from a normally distributed population resulted in the following sample value: 107 109 99 91 103 105 105 94 107 94 97 113 Use the sample information to


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

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

Multiple Regression and Model Building: Zebra Wild Game advertising expenditures

See attached file. The Zebra Wild Game Company sells exotic game to high end restaurants throughout the Far East. The sales manager wants to determine what, if any, relationship exists between the pounds of game sold by 24 sales persons and two independent variables, namely, the advertising dollars spent (in hundreds of tho

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: Difference in spending on textbooks at 2 universities

Please help with the following problem. Independent random samples taken on two university campuses revealed the following information concerning the average amount of money spent on textbooks during the fall semester. Develop a 95% confidence interval for the difference in spending on textbooks between students at Univ

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

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

Random Sample of Household Batteries for Lifetime Hours

See attached data file. Text: Data Analysis & Decision Making with Microsoft® Excel, Rev 3e, S. Christian Albright, Wayne L.Winston, Christopher J. Zappe Chapter 10 - Problem 16 A large buyer of household batteries wants to decide which of two equally priced brands to purchase. To do this, he takes a random sample of 1

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