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Confidence Interval

Margin of Error and Confidence Interval Assumptions

1. To estimate the average time it takes to assemble a certain computer component, the industrial engineer at an electronic firm timed 40 technicians in the performance of this task, getting a mean of 12.73 minutes and a standard deviation of 2.06 minutes. a. What can we say with 99 % confidence about the maximum error if x-

Confidence Interval of Test Score Sample

See attached file for clarity. 1. The standard deviation of test scores on a certain achievement test is 10.7. A random sample of 60 scores on this test had a mean of 76.2. Based on this sample, find a 90% confidence interval for the true mean of all scores. Then answer: What is the lower limit of 90% confidence interval

Confidence Interval of a Random Sample

In a random sample of 225 students at a university, 180 stated that they were nonsmokers. Based on this sample, compute a 95% confidence interval for the proportion of all students at the university who are nonsmokers. Carry your intermediate computations to at least three decimal places. Round your answers to two decimal pl

Confidence Interval For Population Standard Deviation

Pilots who cannot maintain regular sleep hours due to their work schedule often suffer from insomnia. A recent study on sleeping patterns of pilots focused on quantifying deviations from regular sleep hours. A random sample of 20 commercial airline pilots was interviewed, and the pilots in the sample reported the time at which t

Hypothesis Testing & Confidence Interval explained in this answer

A medical researcher estimates that no more than 55% of the U.S. adults eat breakfast every day. In a random sample of 250 U.S. adults, 56.4% say that they eat breakfast every day. At alpha =.01, is there evidence to reject the researcher's claim ? A) Test Statistic B) Graph C) Conclusion D) Construct a 99.9% C.I.

Confidence Interval Estimate using t-Distribution

The level of various substances in the blood of kidney dialysis patients is of concern because kidney failure and dialysis can lead to nutritional problems. A researcher performed blood tests on several dialysis patients on 6 consecutive clinic visits. One variable measured was the level of phosphate in the blood. Phosphate leve

Statistics: Hypothesis Test, Confidence Interval Approach

1. In 2001, the U.S. Department of Labor reported the average hourly earnings for U.S. production workers to be $14.32 per hour. A sample of 75 production workers during 2003 showed a sample mean of $14.68 per hour. Assuming the population standard deviation is $1.45, can we conclude that an increase occurred in mean hourly earn

Statistics: Chapter 8, P23, P34' Chapter 9, P35, P33

Chapter 8 34. Information from the American Institute of Insurance indicates the mean amount of life insurance per household in the United States is $110,000. This distribution follows the normal distribution with a standard deviation of $40,000. a) If we select a random sample of 50 households what is the standard error of

7-12 confidence interval estimate of the population mean

7-12. Twelve different video games showing substance use were observed and the duration times of game play (in seconds) are listed below. The design of the study justifies the assumption that the sample can be treated as a simple random sample. Use the data to construct a 99% confidence interval estimate of (u), the mea durati

Normal, Samples Probabilities and Confidence Interval and Hypothesis Testing.

1- It has been reported that the mean income of parents of freshmen entering a particular university is $91,600. The president of a neighboring university feels that the mean income of the parents of his university's freshman class have a mean income greter than $91,600. The president selects 100 families randomly and finds the

Probability, Confidence Interval

Please show all work. 1. Suppose the salary of assembly line workers has Normal distribution with mean of $20,000, and standard deviation of $3,000. a) What is the probability that a randomly selected assembly line worker earns more than $22,000? b) What is the probability that the average salary of 5 assembly line

Proportion of US citizens living where carbon monoxide levels are acceptable

1.) From a sample of 1201 U.S. citizens, it was discovered that 1139 lived in neighborhoods with acceptable levels of cabon monoxide. A) Obtain a point estimate for the proportion of U.S. citizens who live in neighborhoods with acceptable levels of carbon monoxide. B) Construct a 98% Confidence Interval for the proportio

Anxiety score for today's children; Doctor visits of dog owners

10. Standardized measures seem to indicate that the average level of anxiety has increased gradually over the past 50 years. In the 1950s, the average score on the child manifest anxiety scale was µ=15.1. A sample of n=16 of today's children produces a mean score of M=23.3 with SS=240. a. based on the sample, make a point es

Confidence Interval Estimate of standard deviation of amounts

Listed below are (in micrograms per cubic meter, or mg/m3) in the air. An organization has established an air quality standard for lead of 1.5 mg/m3. The measurements shown below were recorded at a destroyed building on different days immediately following its destruction. Assume that this sample is a simple random sample obtai

Statistics Problems

8. Assume that the salaries of elementary school teachers in the United States are normally distributed with a mean of $34,000 and standard deviation of $2000. What is the cutoff salary for teachers in the bottom 10%? 9. The lengths of pregnancies are normally distributed with a mean of 267 days and a standard deviation of 15

Normal Probability, Samples and Confidence intervals

1- The EMT industry reports that the average time it takes to respond to an emergency call is 25 minutes. Assume that is time is normally distributed with a sigma of 4 minutes. What percentage of call will be responded to in less than 20 minutes? 2- To qualify for the Police Academy, a candidate must score the top 15% on the

10 Problems on Descriptive Statistics, Point Estimates and Confidence Interval

1. Use the confidence interval to find the estimated margin error. Then find the sample mean. A biologist reports a confidence interval of (1.8, 3.0) when estimating the mean height (in centimeters) of a sample of seedlings. The estimated margin of error is______. The sample mean is _________. 2. You work for a consume

Constructing confidence intervals

We will be constructing confidence intervals for the proportion of each color as well as the mean number of candies per bag. Use the methods of 6.3 for the proportions and 6.1 for the mean. If calculating by hand, be sure to keep at least 4-6 decimal places for the sample proportions to eliminate large rounding errors.

Margin of error and the confidence interval

6.10 Margin of error and the confidence interval. A study based on a sample of size 25 reported a mean of 93 with a margin of error of 11 for 95% confidence. (a) Give the 95% confidence interval. (b) If you wanted 99% confidence for the same study, would your margin of error be greater than, equal to, or less than 11? Expl

Calculation of Confidence Interval and Sample Size

Please show work, step by step. 1) Suppose a fast food restaurant wishes to estimate average sales volume for a new menu item. The restaurant has analyzed the sales of the item at a similar outlet and observed the following results: X = 500 (mean daily sales) s = 100 (standard deviation of sample) n = 50 (sample size)

Confidence Interval for Mean: Baseball Data

Please see the attached spreadsheet: With the data I need to answer the following: A)Develop a 95 percent confidence interval for the mean number of home runs per team B)develop a 95 percent confidence interval for the mean number f errors committed by each team C) Develop a 9 percent confidence interval for the mean

Question about Confidence Interval & Sample size

1. A promotion campaign is being planned to encourage people to reduce heat in their homes. In order to measure the campaigns impact, we want to determine the proportion of people who reduce their heat at night. A telephone sample will be taken before and after the campaign. A. What sample size is required if an accuracy of +/-

Proportion, confidence level, standard deviation, population variance

Please see attached 14 Questions. 1. An auditor wants to estimate what proportion of a bank's commercial loan files are incomplete. The auditor randomly samples 100 files and finds 9 are incomplete. Using a 95% confidence interval, estimate the true proportion of incomplete files for ALL the bank's commercial loans. 2.

M&M project: Construct a 95% Confidence Interval for Proportion

M&M Project: Part 3 Use the M&M data to complete this assignment. StatCrunch can be used to assist with the calculations. A link for StatCrunch can be found under Tools for Success in Course Home. Here is also a link: http://statcrunch.pearsoncmg.com/statcrunch/larson_les4e/dataset/index.html. Submit your answers in Exce

Statistics: Five Word Problems

1) The owner of a fish market has an assistant who has determined that the weights of catfish are normally distributed, with mean of 3.2 pounds and standard deviation of 0.8 pound. What percentage of samples of 4 fish will have sample means between 3.0 and 4.0 pounds? 2) A survey of working women in North America was conduct

Statistics: Problems

1. For a t distribution with 16 degrees of freedom, find the area, or probability, in each region. a. To the right of 2.120. (Use 3 decimals.) __________ b. To the left of 1.337. (Use 2 decimals.) __________ c. To the left of -1.746. (Use 2 decimals.) __________ d. To the right of 2.583. (Use 2 decima