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Confidence Interval

Extra Credit work

Number 1 The union for a particular industry has determined that the standard deviation of the daily wages Find a 90% confidence interval for the true mean daily wage of all union workers in the industry. Then complete the table below. Carry your intermediate computations to at least three decimal places. Round your answers

Construct 95% Confidence Interval

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

Confidence interval: Use of Blackberries by students at OSU

Suppose you have drawn a simple random sample of 225 students from OSU. In this sample, 45 students own Blackberries. Let π denote the proportion of OSU students who own Blackberries. Construct a 95% confidence interval for π. Suppose you have drawn a simple random sample of 100 students from OSU and recorded

Margin of error for cost of wedding

Bride's magazine reported that the mean cost of a wedding is $25,000. Assume that the population standard deviation is $8400. Bride's plans to use an annual survey to monitor the cost of a wedding. Use 99% confidence. What is the recommended sample size if the desired margin of error is $651?

Calculations of Margin of Error

A national Retail Foundation survey found housholds intended to spend an average of $932 during the December holiday season. Assume that the survey included 850 households and that the standard deviation of the sample is $215. A With 95% confidence, what is the margin of error?

Variance, estimator for mean, millionaire net worth

#1 Suppose you are sampling from a population with mean µ = 1,065 and standard deviation σ = 500. The sample size is n = 100. What are the expected value and the variance of the sample mean X? Show and explain your work (study guide # 5-41). #2 Suppose a new estimator for the population mean is discovered. The new

Statistics-confidence intervale

1. Given the values of x calculate the standard error of the mean 13 12 9 15 11 16 17 8 12 7 12 2. Given the above numbers calculate the standard error of the mean 3.Given the following data, construct a 95% confidence intervale _ Statistic X S n a Value 113 15 9 .05 4. Constru

Confidence Intervals

Please help me create and interpret the confidence intervals- 90%, 95%, and 99%.. 1)Compute the confidence interval(s) for the attached data (data and graphs)Distance only. 2)Provide graph and table in excel 3)Based on the confidence interval(s), determine if you would change the conclusion that distance does affect a home

Point Estimates & Confidence Interval

A simple random sample of 8 employees is selected from a large firm. For the 8 employees, the number of days each was absent during the past month was found to be 1, 3, 3, 3, 1, 5, 4, and 3 (a) What is the point estimate for , the mean number of days absent for the firm's employees? Round your answer to nearest hundredth. =

Confidence interval

A human resource manager for Carver County is evaluating a recent effort to improve the health of the county's firefighters by providing an exercise room in each of the county's firehouses. Their records prior to installing the exercise rooms indicate that the mean weight of all county firefighters is 198 pounds with a standard

Hypothesis Testing and Confidence Interval Problem

A. *HT* A test was conducted to compare the wearing quality of the tires produced by two tire companies. A random sample of 16 cars is equipped with one tire of Brand X and one tire of Brand Y (the other two tires on each car are not part of the test), and driven for 30 days. The following table gives the amount of wear in thous

Statistcs: Phone Directory and Popcorn Kernels Statistics

Question 1: A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech Pages Plus Yellow Pages. On each page, the mean area devoted to display ads was measured (a display ad is a large block of multicolored illustrations, maps, and text). The data (in square millimeters) are shown below:

Standardized test of manual dexterity

You have administered a standardized test of manual dexterity to two groups of 10 semi skilled workers. One of these two groups of workers will be employed by you to work in a warehouse with many fragile items. The higher the manual dexterity of a worker the less likelihood that worker will break significant inventory. Because o

Standard Deviation

The lifetime of a certain brand of battery is known to have a standard deviation of 11.5 hours. Suppose that a random sample of 50 such batteries has a mean lifetime of 34.5 hours. Based on this sample, find a 90% confidence interval for the true mean lifetime of all batteries of this brand.

Confidence Interval

(1) The lifetime of a certain brand of battery is known to have a standard deviation of 19.8 hours. Suppose that a random sample of 50 such batteries has a mean lifetime of 40.9 hours. Based on this sample, find a 95% confidence interval for the true mean lifetime of all batteries of this brand. Then complete the table below.

Statistics: Set of five questions

See attached file for 5 questions: Mean weight of carry-on luggage Mean of a population Lifetimes of washing machines Proportion of Democrats in sample of registered voters Proportion of customers who use stor credit card for purchases In order to determine the average weight of carry-on luggage by passengers in airpla

Statistics Problems

1. Find the indicated critical z value. Find the value of zα/2 that corresponds to a confidence level of 97.80%. 2. Find the appropriate minimum sample size. You want to be 95% confident that the sample variance is within 20% of the population variance. 4. Express the confidence interval using the indica

Confidence level for variance

You randomly select and measure the contents of 10 bottles of cough syrup. The results (in fluid ounces are shown. 4.216 4.292 4.252 4.244 4.186 4.281 4.269 4.243 4.222 4.231 Assume the sample is taken from a normally distributed population. Construct 98% confidence intervals for (a) σ2 the population

Confidence Interval for Mean Blood Pressure

A researcher wishes to determine whether people with high blood pressure can reduce their blood pressure by following a particular diet. Use the sample data below to test the claim that the treatment population mean mu_1 is smaller than the control population mean mu_2. Test the claim using a significance level of 0.01. You m

Statistics Module: Correlation and Regression

Module 6: Correlation and Regression A For the supermodel dataset at the right, treat height as the explanatory variable and weight as the response variable. (Data set is given in the excel file) 1 Is there a significant correlation? Show the null hypothesis, df and the test you used. yes/

Hypothesis Testing & Confidence Intervals

Question: A survey of 100 mayonnaise purchasers showed 65 were loyal to one brand. Whereas a survey of 100 bath soap purchasers showed only 53 were loyal to one brand. a) Perform a two tailed test at alpha = .05 b) Form a confidence interval for the difference of proportions, without pooling the samples. Does it include 0?

Construct a 95% Confidence Interval

A random sample of 85 group leaders, supervisors, and similar personnel at General Motors revealed that, on the average, they spent 6.5 years on the job before being promoted. The standard deviation of the sample was 1.7 years. Construct a 95 percent confidence interval.

Confidence Interval and Hypothesis Test

1. A sample of 35 golfers showed that their average score on a particular golf course was 80 with a standard deviation of 6. Answer each of the following (show all work): (A) Find the 95% confidence interval of the mean score for all 35 golfers. (B) Find the 95% confidence interval of the mean score for all golfers if this

Confidence Interval and Standard Deviation: Wage Example

In a random variable of 100 workers you find the average wage is $21.00 per hour and the standard deviation of wage is $4.00 per hour. What is the 99% confidence interval for mean hourly wages? (Note that with n=100 Pr (t.2.364)=0.01 and Pr (t>2.626)=0.005

Confidence Interval for Customer Satisfaction and Testing

Quality Progress, February 2005, reports on the results achieved by Bank of America in improving customer satisfaction and customer loyalty by listening to the voice of the customer. A key measure of customer satisfaction is the response on a scale from 1 to10 to the question: Considering all the business you do with Bank of

Confidence Interval & Sample Size for a Random Sample

1 (b). A survey of a random sample of 250 car commuters indicates that 80 would switch to commuting by public transport if they had to pay at least $10 per week for parking at their work places. (i) Using a 95% confidence level, calculate the confidence interval for the proportion of the commuters who might be expected to ch

Statistics: Confidence Interval for Mean

* The UNITE/MORI 2004 survey of student experiences estimated that university students in the UK paid on average $54 per week in accommodation costs. Assume that this average is based on a sample 755 students and that the population standard deviation for weekly accommodation costs is $ 11. a. Construct a 90 per cent confi

Confidence Interval: Proportion of Drug Test

As a condition of employment, Fashion Industries applicants must pass a drug test. Of the last 220 applicants 14 failed the test. Develop a 99 percent confidence interval for the proportion of applicants that fail the test. Would it be reasonable to conclude that more than 10% of the applicants are now failing the test? In addit

Assessing Sample Size for the Number of "Walk-Ins"

Part of my job description is to teach Recruiters their daily individual tasks and how to properly manage their time. One of the Recruiter duties is to generate appointments in many different ways. They can visit high schools, Shopping Centers, or any other public places available within their Recruiting zone; their main goal

Confidence Interval

1. In each of the following exercises, a set of condition is given. To construct a 95 percent confidence interval for the population mean, would you use the z distribution, a t distribution, or neither? Where appropriate, determine the z or t value. n = 21, xbar = 23.1, s = 7.5, population distribution shape normal, σ = 7.