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Confidence Interval

Confidence Intervals and Significance Levels

68. In a study, Germination and Emergence of Broccoli, conducted by the Department of Horticulture at Virginia Polytechnic Institute and State University, a researcher found that at 5°C, 10 seeds out of 20 germinated, while at 15°C, 15 out of 20 seeds germinated. Compute a 95% confidence interval for the difference between t

Confidence Interval: Breaking Strengths of Cables

The breaking strengths of cables produced by a certain manufacturer have a standard deviation of 82 pounds. A random sample of 150 newly manufactured cables has a mean breaking strength of 1950 pounds. Based on this sample, find a 95% confidence interval for the true mean breaking strength of all cables produced by this manufact

Sample Size for Mean and Proportion Football Team

Part I. Suppose the coach of the football team wants to estimate the proportion of the population of fans who support his current starter lineup. The coach wants the estimate to be .04 of the true proportion. Assume a 99 percent level of confidence. The coach estimated the proportion supporting the current starter lineup to

Confidence Intervals and Biased Estimators

6. The heights of a random sample of 50 college students showed a mean of 174.5 cm and standard deviation of 6.9 cm. a) Construct a 98% confidence interval for the mean height of all college students. b) What can we assert with 98% confidence about the possible size of our error if we e

How do you find the population proportion for the Fox TV network?

How would I find the population proportion for this example? The Fox TV network is considering replacing one of its prime-time crime investigation shows with a new family-oriented comedy show. Before a final decision is made, network executives commission a sample of 400 viewers. After viewing the comedy, 250 indicated they w

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 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