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Confidence Interval

10 problems on Confidence Intervals solved using MINITAB

1. An environmental group at a local college is conducting independent tests to determine the distance a particular make of automobile will travel while consuming only 1 gallon of gas. A sample of five cars is tested and a mean of 28.2 miles is obtained. Assuming that the standard deviation is 2.7 miles, find the 95% confidence

Hypothesis Testing and Confidence Interval..

See attached file. Statistics Failure and reliability problem. A tire supplier claims that the tread life of its tyres has a mean of 32000 miles. The buyer has doubts. State the suitable null and alternative hypothesis to test this claim. A testing agency randomly selects 25 vehicles. He puts the new tyres on the vehicle

Point Estimate and Confidence Interval

James Jackson, owner of James Contracting Company, is worried about shipping costs and admin costs that incur with small purchase orders. So they reduce spending in this area, he created an incentive plan for orders over $40 so that hey may encourage customers to lower the # of small orders into bigger orders. This is the amount

Inferences Involving two populations

Inferences concerning the mean difference using two dependent samples, two independent samples, and proportions. A. Before 93 106 87 92 102 95 88 110 After 92 102 89 92 101 96 88 105 a. What is the point estimate for the mean reduction in the diastolic reading? b. Find the 98% confidence inter

Statistics calculations for brown bullheads in Great Lakes

Review questions below and indicate which confidence interval statistic you would use in each case (z-sigma, Z-s, or t-s): Brown bullheads are a common Great lakes feeding fish and indicator species for sediment health. The current study focused on the weight of fish taken in various locations. a. A sample of 27 brown bull

Construct Confidence Level of mobile home owners and their cell phone providers

A survey of 4,581 U.S. households that owned a mobile phone found that 58 percent are satisfied with the coverage of their cellular phone provider. Assuming that this was a random sample, construct a 90 percent confidence interval for the true proportion of satisfied U.S. mobile phone owners. (Round intermediate calculations

Confidence Interval for Mean National Student Loan Survey

The National Student Loan Survey collects data to examine questions related to the amount of money that borrowers owe. The survey selected a sample of 1280 borrowers who began repayment on their loans between 4 and 6 months prior to the survey. The mean debt for undergraduate study was $18,900 and the standard deviation was abou

Case Study: Mean Overall Duration of Symptoms & Confidence Interval

Twenty-five volunteers who had developed cold symptoms within the last 24 hours were given zinc lozenges to take every 2 to 3 hours until their cold symptoms were gone. The mean overall duration of symptoms was 4.5 days with a standard deviation of 1.6 days. The selected cases have a distribution which appears to be symmetri

Stat Tutorials please

Q.8.1 Southside Hospital in Bay Shore, New York, commonly conducts stress tests to study the heart muscle after a person has a heart attack. Members of the diagnostic imaging department conducted a quality improvement project to try to reduce the turn-around time for stress tests. Turn around time is defined as the time from w

Sampling populations give 95% confidence intervals

Please give answers with steps. 1) The accounting firm of Ahmadi & Associates was commissioned to audit a population of 500 accounts. For this audit, Ahmadi & Associates selected a simple random sample of 64 accounts. The sample showed a mean discrepancy of $120 with a standard deviation of $24. Develop an approximate 95% co

Confidence Interval Calculations

1. Nancy Joon, Inc. has 1500 employees. A simple random sample of 81 employees was selected and the individuals I the sample were asked how much they contribute monthly to their retirement accounts. The mean amount for the sample was $150 with a standard deviation of $45. Develop an approximate 95% confidence interval for the me

Analyze Unusual Baby Growth Patterns using Confidence Intervals

In order to identify baby growth patterns that are unusual, we need to construct a confidence interval estimate of the mean head circumference of all babies that are 2 months old. a random sample of 100 babies is obtained and the mean head circumferene is found to be 40.6cm. Assuming that the population standard deviation is kno

Confidence Interval for Population Proportion..

Please solve the exercise below using Excel and show your work (with formulas). The production manager for the XYZ Manufacturing company is concerned that the customer orders are being shipped late. He asked one of his planners to check the timeliness of shipments for 1000 orders. The planner randomly selected 1000 orders and

Construct a 99 Percent Confidence Interval Around the Mean

A small town has a population of 20,000 people. Among these, 1,000 regularly visit a popular local bar. A sample of 100 people who visit the bar is surveyed for their annual expenditures in the bar. It is found that on average each person who regularly visits the bar spends about $2000 per year in the bar with a standard deviat

Hypothesis Tests & Confidence Intervals

In the 1980s, Tennessee conducted an experiment in which kindergarten students were randomly assigned to "regular" and "small" classes, and given standardized tests at the end of the year. ("Regular" classes contained approximately 24 students and "small" classes contained approximately 15 students.) Suppose that, in the popul

Statistics: Memo to Universal Credit team about sample size

See the attached file. A partner company to American Intellectual Union (AIU), Universal Credit Inc., would like to examine the required sample size needed to be able to estimate the mean dollars that each card holder will spend each month. It would like to be within plus or minus $55 of the true mean with a 95% confidence le

Hypothesis test for proposed product of a notebook computer company

See attachment for format. 11.28 When companies are designing a new product, one of the steps typically taken is to see how potential buyers react to a picture or prototype of the proposed product. The product-development team for a notebook computer company has shown picture A to a large sample of pot

Confidence Interval For Mean Price And Age Of Bank Employees

Please see attachment for data. 1. To find the confidence interval for the true mean of the "price in $000" of all the employees in the bank, should the z-score or t-score be used?if so why? 2. Find a 95% and a 99% confidence level for "price in $000" and "age" respectively using all the 80 data given that the population v

Solve: Using the Confidence Interval for the Mean

In New York State, savings banks are permitted to sell a form of life insurance called the savings bank life insurance (SBLI). The approval process consists of underwriting, which includes a review of the application, a medical information bureau check, possible requisites for additional medical information and medical exams, a

Confidence Interval for the Mean and Proportion

Scenario: A market researcher for a consumer electronics company wants to study the television viewing habits of residents of a particular area. A random sample of 40 respondents is selected, and each respondent is instructed to keep a detailed record of all television viewing in a particular week. The results are as follows:

Confidence Interval & Hypothesis Testing: Proportion

The topic of my project is to find out the number of patients that have used In Home Care as their home health agency for more than 2 years. In Home Care's goal is to have over 50% of their patients be with them over 2 years which would demonstrate the staff is providing adequate and satisfying healthcare to their patients. A s

Normal Probability, Hypothesis Testing & Confidence Interval

See attached file for proper formatting. Please show work. From the book (Statistical Techniques in Business and Economics) By D. A. Lind/ W. G. Marchal/ S. A. Wathen. Chapter 8 1. Packages of sugar bags for Sweeter Sugar Inc. have an average weight of 16 ounces and a standard deviation of 0.24 ounces. The weights

Confidence intervals for proportions of wrist injuries

A study of injuries to in line skaters used data from the National Electronic Injury Surveillance System, which collects data from a random sample of hospital emergency rooms. The researchers interviewed 161 people who came to emergency rooms with injuries from in line skating. Wrist injuries (mostly fractures) were the most c

Confidence Interval for Mean and Proportion..

See attached file. Please show the formula and step used to solve these two problems. 3. A random sample of 10 parking meters in downtown Nashville showed the following incomes for a day. $2.60, $1.05, $2.45, $2.90, $1.30, $3.10, $2.35, $2.00, $2.40, $2.35 Find the 95% confidence interval of the true mean. 6. Out

Inference about a population proportion: Times New Roman and Gigi preference

Plain type fonts such as Times New Roman are easier to read than fancy fonts such as Gigi. A group of 25 volunteer subjects read the same text in both fonts. (This is a matched pairs design. One sample procedures for proportions, like those for means, are used to analyze data from matched pair designs.) Of the 25 subjects, 1

Sample Size & Margin of Error

An automobile manufacturer would like to know what proportion of its customers are not satisfied with the service provided by the local dealer. The customer relations department will survey a random sample of customers and compute a 99% confidence interval for the proportion who are not satisfied. (a) Past studies suggest t