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Confidence Interval

Confidence interval for mean

a random sample of 50 engineers of a large technology company that the sample mean is 34.4 year. assume that the population standard deviation is 8 years. construct and explain a 98% confidence interval estimate of the average age of all engineers employed by the company.

Confidence interval for mean of large equipment rental

a large equipment rental company wants to estimate the mean number of days a piece of equipment is rented out. a random sample of 12 recent rentals shows a mean of 2.14 days and a standard deviation of 1.29 days. construct and explain a 99% confidence interval estimate of the population mean number of rental days for this type o

Confidence interval for population proportion of pizza

in order to determine the population proportion of pizza restaurants that offer a salad bar a random sample of 1250 of these restaurants was selected from across the us. if 997 of the sampled restaurants offered a salad bar, construct and explain a 95% interval estimate of the proportion of all pizza restaurants in the us with

Statistics: Basics and Confidence Intervals

The Ohio Department of Agriculture tested 203 fuel samples across the state in 1999 for accuracy of the reported octane level. For premium grade, 14 out of 105 samples failed (They didn't meet ASTM specifications and the FTC Octane posting rule). Therefore, how many samples would be needed to create a 99% confidence interval tha

Basics and Confidence Intervals 6

The coffee/soup machine at the local bus station is supposed to fill cups with 6 ounces of soup. Ten cups of soup are brought with results of a mean of 5.93 ounces and a standard deviation of 0.13 ounces. How large a sample of soups would we need to be 95% confident that a sample mean is within 0.03 ounces of the populat

Calculating a 90% Confidence Interval

A federal bank examiner is interest in estimating the mean outstanding defaulted loans balance of all defaulted loans over the last three years. A random sample of 20 defaulted loans yielded a mean of $67,918 with a standard deviation of $16,552.40. Calculate a 90% confidence interval for the mean balance of defaulted lo

Confidence interval for mean computing

In manufacturing process a random sample of 36 bolts manufactured has a mean length of 3 inches with a standard deviation of .3 inches. What is the 99% confidence interval for the true mean length of the bolt? = [ ]

Determining the Confidence Interval for Mean: Example

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 sample standard deviation is 2.7 miles, find the 95% con

confidence interval for the mean

2) Constructing a confidence interval for the mean. M&M Candies Use the following data of the weight in grams of M&M plain candies. Assume the population is normally distributed. **Hint: copy and paste the data into excel. Then use excel to find the sample mean and sample standard deviation you will need to complete the fo


AluminiCorp is a major producer of aluminum cans that produces 40 billion aluminum cans every year. You work as a quality control officer for AluminiCorp, and are responsible for ensuring that the aluminum cans produced meet certain specifications. Each can is supposed to consist of precisely 15 grams of aluminum, and the ma

Statistics problems

Problem Set 1: Chapter 12, problems 2, 4, 6, 12; Chapter 13, problems 4, 10, 14, 20, 26 Chapter 12 2. Explain why it would not be reasonable to use estimation after a hypothesis test for which the decision was to 'fail to reject Ho". 4. A researcher has constructed an 80% confidence interval of mu = 45 +/- 8, using a

Confidence Interval for Mean:Marriage rate of Harvard alumni

1. The Harvard class of 1957 had a reunion attended by 36. Among them, they discovered that they had been married an average of 2.6 times. From the Harvard Alumni Register, the dean learned that the standard deviation for alumni was 0.3 marriages. Help the dean construct a 99% confidence interval for the marriage rate for Ha

Confidence Interval for Mean Difference.

1. 12 mature citrus trees of one variety and 15 of another gave means and standard deviations of their heights as 13.8 and 12.9 ft (means), and 1.2 and 1.5 ft (standard deviations). Find a 95% confidence interval for the true difference in average heights between all trees of the first and the second variety. Would you be able

Confidence Interval for Mean: Child Manifest Anxiety Scale

Standardized measures seem to indicate that the average level of anxiety has increased gradually over the past 50 years. In the 1950's average score on the Child Manifest Anxiety Scale was u= 15.1. A sample on n =16 of today's children produces a mean score of M=23.3 with SS= 240. Interpret the confidence level I canno

Confidence Interval Conducted for Mean Tears

1.Compute a 95% confidence interval for the mean saline of the tears. You select a random sample of 100 tear drops. The sample has an average salt concentration of 0.1 with a standard deviation of 0.01. 2. In class a poll was conducted that I will get 60% of my work correct. To be 95% confident that I am within 2% of the v

Confidence interval for mean of random sample

A random sample of 16 Google managers yield the following information on annual salaries. The sample mean is $69,000, with a sample standard deviation of $4,000 1)How many google managerswould need to be selected to generate a 95%confidence interval with a margin of error of plus or minus $1000.

Creating and interpreting confidence intervals

Tesla Motors needs to buy axles for their new car. They are considering using Chris Cross Manufacturing as a vendor. A random sample of 250 axles yields 240 that met Tesla's specifications. a) Determine the 99% confidence interval for the population proportion of criss cross axles that meet Tesla's specifications. b) Int

Confidence Interval and Sample Size Calculations

1. Of 300 people waiting lunch at a department store cafeteria, 102 had dessert. What is the confidence associated with a Rao score interval of length .1 (i.e., margin of error .05)? 2. Calculate the sample size necessary to estimate the proportion of drivers that exceed the spend limit on a stretch of a road between Bakersfi

Hypothesis Testing & Confidence Interval for Mean

Children's scores on a measure of aggression are known to have a normal distribution, with a mean of 50 and a standard deviation of 6. A researcher takes a random sample of 49 children, has them listen to calming music for 4 hours, and then measures the aggression level of this sample of children. The sample has a mean of 51.

Probability: Test ages of students, average GPA, finance majors

See attached files. Use the Student_Data.xls file which consists of 200 MBA students at Whatsamattu U. The file includes variables regarding students' age, gender, major, GPA, Bachelors GPA, course load, English speaking status, family, weekly hours spent studying. Each of the three assigned problems should be formatted as a

Confidence interval and sample mean

Find the sample size required to estimate the mean age of registered drivers in the United States. Assume that we want 95% confidence that the sample mean is within 1/2 year of the true mean age of the population. Also assume the standard deviation of the population is known to be 12 years.

Descriptive Statistics & Confidence Interval

Please see attached files. 1. The figure below shows the probability histogram for the total number of spots when a die is rolled eight times. The shaded area represents the chance that the total will be between__ _ and ___ (inclusive). 8. A coin is tossed 100 times. True or false, and explain: (a) The expected value fo

Confidence Interval Explanation

1) To aid in planning the development of a tourist shopping area, a state agency wants to estimate the average dollar amount spent by a tourist in an existing shopping area. A simple random sample of 56 tourists gave an average of $258 with standard deviation of $85. a) Give a 95% confidence interval for the average of the p

Identify outcome of the following Polls.

POLL: OBAMA, MCCAIN LEAD IN N.H. HUCKABEE NOT SEEING GAINS FROM IOWA WIN ALL EYES ON NEW HAMPSHIRE; TOP CONTENDERSâ?? HOPES PIVOT ON FIRST PRIMARY ELECTION 2008: How the voters upended pollsters Pollsters the most shocked at New Hampshire outcome Read all of the articles, noting when the articles were written, which

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