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Confidence Interval

Proportion of Students on Financial Aid

A university dean is interested in determining the proportion of students who receive some sort of financial aid. Rather than examine the records for all students, the dean randomly selects 200 students and finds that 118 of them are receiving financial aid. Use a 99% confidence interval to estimate the true proportion of stud

Assume that the heights of women are normally distributed.

Assume that the heights of women are normally distributed. A random sample of 20 women have a mean height of 62.5 inches and a standard deviation of 1.3 inches. Construct a 98% confidence interval for the population variance, (lower case sigma)2. a.(0.9,2.1) b.(0.9,4.4) c.(0.7,3.2) d.(0.9,4.2)

Hypothesis Claim Testing

1. At a large publishing company, the mean age of proofreaders is 36.2 years with a standard deviation of 3.7 years. Assuming the age is normally distributed, find the following: a. If a proofreader is selected at random what is probability his/her age will be between 36 and 38 years. b. If a random selected sample 20 proofrea

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

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

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

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

Statistics Multiple Choice

1. 1,600 of 2,000 voters say they plan to vote Republican. Use 0.95 degree of confidence to find the popltn proportion interval. A. 69.2 to 86.4% B. 76.5 to 83.5% C. 77.7 to 82.3% D. 78.2 to 81.8% E. none of the above 2. The mean weight of trucks traveling on the the highway is unknown. A state highway inspec

Develop a 95% confidence interval estimate for the mean of the population

1. An printout of the descriptive measures of daily checking account balances (in $) of bank customers is shown below. Develop a 95% confidence interval estimate for the mean of the population of the checking balances. Account Balance Information Mean 4828.29 Median 5115.25 Mode 4976.50 Standard Deviation 1143.57 Sampl

Statistics: Comparisons Involving Means and confidence interval

FedEx and United Parcel Service (UPS) are the world's two leading cargo carriers by volume and revenue. According to the Airports Council International, the Memphis International Airport (FedEx) and the Louisville International Airport (UPS) are two of the ten largest cargo airports in the world. The following random samples (in

Confidence Intervals and Margin of Error

Need assistance setting up and solving this problem: The National Center for Education Statistics reported that 47% of college students work to pay for tuition and living expenses. Assume that a sample of 450 college students was used in the study. a. Provide a 95% confidence interval for the population proportion of colleg

Number of Respondents Required

In a public opinion poll 48% of 189 respondents favor an elimination of taxes on dividend income. How many respondents would be needed to calculate a 95% confidence interval (for the proportion of people who favor an elimination of taxes on dividend income) that has a total width no greater than 4% (the estimate must be within +

Statistics - 95% error margin and 98% confidence interval

1. A company wishing to improve its customer service collected hold times from 75 randomly selected incoming calls to its hot line that were put on hold. These calls had sample mean hold time = 3.4 minutes and s = 2.3 minutes. Is the claim that μ > 3.0 minutes substantiated by these data? Test with α = .05. 8.95

95% confidence interval - statistics

Hack Wilson¿s major league record of 190 runs batted in during a single season in professional baseball has stood for 70 years. Perhaps the reason for this longevity is that the average for all the other league leaders is so far below the total Wilson knocked in back in 1930. A confidence interval might provide a clue. A random