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Confidence Interval

Computing 90% confidence Interval from 95% confidence Interval alone

Computing from a large sample, one finds the 95% confidence interval for &#956; to be (6.8, 14.2). Based on this information alone, determine the 90% confidence interval for &#956;.

This problem calculates z-scores and confidence intervals (using Chebyshev inequality). It also explains why the z-score of the mean needs to be 0. A number of examples have been provided.

1. Consider an infinite population with a normal shape and a mean of 250 and standard deviation of 30. a. Compute the z-scores for the following values of X and locate each on the graph. X Z-score 200 320 220 270 250 b. According to the Empirical rule what percent of the data should be between 220 and 280? Bet

The problem is related to the sample size calculation. Detailed steps are given with formula for computation.

The Star Tribune, a Min.-St. Paul newspaper sponsored a poll designed to reveal opinions about the "photocop" which consist of cameras positioned to catch drivers who run red lights. The cameras photograph the license plates of cars passing through red lights, and those car owners are later mailed traffic violations. The newspap

Point estimate of the proportion of the population Margin of error 95% confidence interval for the population proportion

Question: Towers Perrin, a New York human resources consulting firm, conducted a survey of 1100 employees at medium sized and large companies to determine how dissatisfied employees were with their jobs (The Wall Street Journal, January 29, 2003). A total of 473 employees indicated they strongly disliked their current work ex

Overdue Promotion Hypothesis Testing

Part 1: A study was conducted to see if more than 60% of the American corporate work force felt that they were overdue for a promotion. A random sample of 1500 Americans currently working in a corporate atmosphere was taken. 855 said that they did feel that a promotion was overdue. A 95% confidence interval for estimating t

Confidence Intervals: Large Sample

When would I want a small confidence interval and when would I be satisfied with a larger one? When is a larger sample important?

Confidence Intervals and Probability : Sampling without Replacement

Suppose that 55 percent of the people in a population of 500,000 support your candidate. If you conduct a poll of 1,000 people, what is the interval that has a 95 percent chance of containing the results of your poll? Suppose you have 60 red marbles and 40 blue marbles in a box. If you pick out 10 marbles without replacemen

Statistics - Multiple Choice Questions

See attached file for full problem description. 1. The standard normal distribution a. is a special case of the normal distribution b. has a mean equal to 0 and a standard deviation equal to 1 c. measures the distance from the mean in units of the standard deviation d. all of the above 2. Any normal distribution

Students t test with Confidence Intervals

Body mass index is calculated by dividing a person?s weight by the square of his or her height; it is a measure of the extent to which the individual is overweight. For the population of middle-aged men who later developed diabetes mellitus, the distribution of baseline body mass indices is approximately normal with unknown mean

Confidence Interval

In order to compare the means of two populations, independent random samples of 400 observations are selected from each population, with the following results: Sample 1: xbar = 5,275 s= 150 Sample 2: xbar = 5,240 s= 200 a. Use a 95% confidence interval to estimate the difference between the population means (?1 - ?2 ).

Constructing a confidence interval for mean age

Constructing a confidence interval - The stemplot below lists the ages of applicants who were successful in winning promotion (based on data from "debating the use of statistical evidence in allegations of age discrimination," by barry and boland, American Statistician, vol 58 no. 2). Assume that the sample is a simple random sa

Testing of hypothesis and 95% Confidence interval

According to a survey conducted in October, 2001, consumers were trying to reduce their credit card debt (Margaret Price, "Credit Debts Get Cut Down to Size," Newsday, November 25, 2001, F3). Based on a sample of 1,000 consumers in October 2001 and in October 2000, the mean credit card debt was \$2,411 in October 2001 as compare

Constructing Confidence Intervals for mean weight

Listed below are weights (in grams) from a sample of bats. Construct a 95% confidence interval estimate of their mean weight. Are the confidence interval limits very different from the limits of 1.56 and 1.87 that are found when assuming that σ is known to be 0.30g ? 1.7 1.6 1.5 2.0 2.3 1.6 1.6 1.8 1.5

Inferences based on two samples

Refer to the data for 308 diamonds saved in the diamonds file. Two quantitative variables in the data set are number of carats and selling price. One of the qualitative variables is the independent certification body that assessed each of the stones. Three certification bodies were used: GIA, IGI, and HRD. The MINITAB print

Statistics Statistical Estimation, Confidence limits for population proportion, 80% confidence limits, 90% confidence limits, 95% confidence limits. Step by step solution to the posted problem.

Question : From a population of 1600 documents a random sample of 100 documents is drawn and found 10 defects in the sample. Find the representative number of defects in the total population of 1600 documents at 80% confidence level, at 90% confidence level and at 95% confidence level. Please see the question file attached.

The U.S. Department of Transportation defines an airline flight as being "on-time" if it landed less than 15 minutes after the scheduled time shown in the carrier's Computerized Reservation System.

The U.S. Department of Transportation defines an airline flight as being "on-time" if it landed less than 15 minutes after the scheduled time shown in the carrier's Computerized Reservation System. Cancelled and diverted flights are counted as late. A study of the 10 largest U.S. domestic airlines found Southwest Airlines to h

What is the degree of confidence? Find the margin of error.

(1) The confidence interval: 5.06 < sigma2 < 23.33 is for the population variance based on the following sample statistics: n = 25, x-bar = 41.2, and s = 3.1 What is the degree of confidence? Use only integers, no % sign and no decimal places. (2) Find the margin of error. 95% c

Statistics - Multiple Choice: estimation, z value, confidence interval, t statistic, point estimate for population proportion, error of the estimation, point estimate of the population variance, chi-square values, sample size

Question 1: When a statistic calculated from sample data is used to estimate a population parameter, it is called : an interval estimate a point estimate a statistical parameter a good guess Question 2: A large appliance company sends out technicians to unpack, assemble, and connect every gas dryer that is sold. I

Margin of error, Confidence interval estimate, Sample size, Point Estimate

Attached please find four Statistics problems. Please answer each question in detail, showing all intermediate steps as well as the final resolution. Problem #4 Fortune Survey A survey of small businesses with Web sites found that the average amount spent on a site was \$11,500 per year (Fortune, March 5, 2001). Given a

95% confidence interval for the population proportion, sample without replacement

1. Ophelia O'Brien, VP of Consumer Credit of American First Banks (AFB), has implemented a 'fast feedback' to keep her informed of the default rate on personal loans at the AFB member banks. On each Friday, the default rate is calculated for a sample of 500 personal loans. Last Friday's sample contained 30 defaulted loans. The 9

Develop a 98 percent confidence interval for the population mean.

An important factor in selling a residential property is the number of people who look through the home. A sample of 15 homes recently sold in the Buffalo, New York, area revealed the mean number looking through each home was 24 and the standard deviation of the sample was 5 people. Develop a 98 percent confidence interval for t

Estimators and Confidence Interval

A certain medication is known to increase the pulse rate of its users. The standard deviation of the pulse rate is know to be 4 beats per minute. A sample of 40 users had an average pulse rate of 98 beats per minute. Find the 95% confidence interval of the true mean (of the population)? Give at least 2 properties of a good es

Sample size estimation and Confidence Interval

1. A student surveys 100 classmates by asking each if they have outstanding loans. After finding the sample of proportion for this sample of n = 100 subjects, can the methods of this section be used to estimate the proportion of all adults who have outstanding loans? Why or why not? 2. Express the confidence interval 0.600 < p

Use Statdisk to find the following confidence interval estimates of the percentage of yellow peas.

1. Mendelian Genetics?When Mendel conducted his famous genetics experiments with peas, one sample of offspring consisted of 428 green peas and 152 yellow peas. a. Use statdisk to find the following confidence interval estimates of the percentage of yellow peas. 99% confidence interval_______________ 98% confidence interval___

Survey Data and Information in the Media

How much does understanding the concept of confidence interval affect the way you draw conclusions from survey data or information presented in the news or media?

See attached file for full problem description. Confidence Intervals 1. For a sample mean of 4 and a population standard deviation of 0.3 with a sample size of 100, find the 95% CI for the population mean. 2. Using Internet Explorer, go to http://www.rossmanchance.com/applets/Confsim/Confsim.html . (It may take a minut

Multiple Choice

1. Compare the results of the large sample with the results from the small sample and explain what they mean. a. As the sample size gets larger, the interval decreases. We become more confident that the mean will lie in our interval. b. As the sample gets larger, the interval increases. We become more confident that the mean

4 Stats Questions

1. The business college computing center wants to determine the proportion of business students who have personal computers at home. If the proportion exceeds 30%, then the lab will scale back a proposed enlargement of its facilities. Suppose 250 business students were randomly sampled and 75 have pcs at home. Find the rejection

Statistics Problem Set

1. To help consumers assess the risks they are taking, the food and drug administration publishes the amount of nicotine found in all commercial brands of cigarettes. A new cigarette has recently been marketed. The FDA tests on this cigarette gave a mean nicotine of content 28.2 milligrams and standard deviation of 2.7 milligram

Point Estimation and Interval estimation

47) Arthur D. Little, Inc. estimates that approximately 70% of mail received by a household is advertisements (Time, July 14, 1997). A sample of 20 households shows the following data for the number of advertisements received and the total number of pieces of mail received during one week. a) What is the point estimate of the