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Confidence Interval

Confidence Intervals, Sample Size, and Confidence Levels

1. Can you give a general rule as to what happens with confidence intervals as a function of sample sizes and confidence levels? What are the trade-offs? 2. Take a sample of something in your work environment, something simple, and calculate a confidence interval. Some possible samples: the average number of people in y

Statistics: Large Sample Confidence Interval for a Population

The lengths of 225 fish caught in Lake Michigan had a mean of 15.0 inches. Assume that the population standard deviation is 2.5 inches. - Give a point estimate for mu, the population mean . - Find the 90% confidence interval for the population mean length.

Confidence Interval

In an effort to compare college costs in State of Michigan, a sample of 36 junior students is randomly selected statewide from the private colleges and 36 more from the public colleges. The private college sample resulted in a mean of $27,650 and the public college sample mean was $11,360. Assume the annual college fees for priv

Hypothesis Test: Mean Yearly Sugar Consumption

The American Sugar Producers Association wants to estimate the mean yearly sugar consumption. A sample of 16 people reveals the mean yearly consumption to be 60 pounds with a standard deviation of 20 pounds. A. What is the value of the population mean? What is the best estimate of this value? B. Explain why we need to use th

T Critical and Confidence Interval

See the attached file. 2) Use Table 4 of the appendix to find tc for a 0.99 confidence level when the sample size is 4. 4) Use Table 4 of the Appendix to find tc for 0.95 confidence level when the sample size is 12. 6) Wildlife: Wolf Pups. The number of pups in the wolf dens of the southwestern United States is recorded b

How do you construct a confidence interva for the true mean ...

A sample of 20 pages was taken without replacement from the 1,591 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: 0 260 356 403 536

Confidence Intervals and Statistics Testings

1. The P-value for a two sided test of the null hypothesis H0: µ = 30 is 0.04. a) Does the 95% confidence interval include the value 30? Why? b) Does the 90% confidence interval include the value 30? Why? 2. The level of calcium in the blood in healthy young adults varies with mean about 9.5 milligrams per deciliter and st

Exercises of Applied Statistics in Business and Economics

Please complete these 2 exercises from Applied Statistics in Business and Economics. 8.46 A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighed on a very accurate scale. The results in grams were 3.087 3.131 3.241 3.241 3.270 3.353 3.400 3.411 3.437 3.477 (a) Construct a 90 percent conf

Confidence interval calculation

1. A quality engineer is responsible for maintaining control of the bottling process in a beer factory. The goals is to maintain the intended volume (6 oz) with as little variation as possible. Since product sampled is not suitable for sale and becomes waste, it is very important to sample a minimal number of bottles. However, i

Standard errors and difference in proportion

1. Find the standard error of the mean for each sampling situation (assuming a normal population). What happens to the standard error each time you quadruple the sample size? a. sigma = 32, n = 4 b. sigma = 32, n = 16 c. sigma = 32, n = 64 2. The American Bankers Association reports that, in a sample of 120 consumer

Compute confidence interval and test population mean

1. Compute the 95% confidence interval on the population mean if a sample of 1000 is taken and the sample mean is found to be 15.95 and standard deviation is 4.2. Interpret the interval. What does it mean? 2. Test to see if a population mean is greater than the assumed (or historical) value of 16. When a sample of 1000

Statistics: Solving for the Confidence Interval

Question: 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: 0

Statistics - Confidence Interval..

Please help with following problems & show how to do work in excel or megastat. 8.60 A certain brand of dry noodles contains a mixture of beet, spinach, carrot, and plain. A random sample of 200 dry noodles contained 47 beet noodles. (a) Construct a 95 percent confidence interval for the true proportion of beet noodles. (b)

Confidence Interval

What does it mean when you apply confidence intervals using a normal distribution?

Significance Tests and Confidence Intervals

Please help with the following problem. Using the data on the table below, are there any correlations between population changes for the areas listed. The following is a list of acceptable tests: regression line and equation; correlation one-sample t-test one-sample t confidence interval matched-pairs t-test two-sa

Hypothesis Testing With a 95% Confidence Interval for Mean

We have created 95% confidence interval for mean; with the result (10, 15). What decision will we make if we test H0 : mean = 16 versus H1 : mean is not equal to16 at alpha = 0.025? Reject H0 in favor of H1. Accept H0 in favor of H1. Fail to reject H0 in favor of H1. We cannot tell what our decision will be from the inform

Increasing the Precision of the Confidence Interval

1. What is the most controllable method of increasing the precision (narrowing) of the confidence interval? 2. What percentage of times will the mean (population proportion) not be found within the confidence interval? 3. When you draw a sample from a normal distribution, what can you conclude about the sample distribution? Ex

Statistics - 3. A sample of 49 households is taken from a population in which the standard deviation is 7. The standard error of the mean isPlease see the attached file. 4. It is desired to construct a 95% confidence interval. The correct value of Z to obtain for the 95% confidence interval is: ... 5. A confidence interval has been constructed with total width of 50 units. If the sample mean is 100, the lower bound of the interval is ... [See the attached questions file.]

3. A sample of 49 households is taken from a population in which the standard deviation is 7. The standard error of the mean isPlease see the attached file. 4. It is desired to construct a 95% confidence interval. The correct value of Z to obtain for the 95% confidence interval is: ... 5. A confidence interval has been const

Mean, Standard Deviation, Count, Confidence Intervals

Assume that the random variable is normally distributed A parking control officer is conducting an analysis of the amount of time left on parking meters. A quick survey of 15 cars that have left their metered parking spaces produced the following times (in minutes). Estimate with 95% confidence the mean amount of time left f

Statistics - Confidence Interval for Estimator

A statistics professor wants to compare today's students with those from 25 years ago. All of his current students' marks are stored on a computer so that he can easily determine the population mean. However, the marks from 25 years ago reside only in his paper files. He does not want to retrieve the marks and will be satisfie

Statistics - Confidence Interval for Production Plant

The operations manager of a large production plant would like to estimate the average amount of time workers take to assemble a new electronic component. After observing a number of workers assembling similar devices, she guessed that the standard deviation is 6 minutes. How large a sample of workers should she take if she wis

Statistics: Proportions and Confidence Interval

Never forget that even small effects can be statistically significant if the samples are large. Of 148 small businesses, 106 were headed by men and 42 were headed by women. During a three-year period, 15 of the men's businesses and 7 of the women's businesses failed. a) Find the proportions of failures for businesses headed

Confidence Interval - (A) 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 ... (B) Biting an unpopped kernel of popcorn hurts! As an experiment, a self-confessed connoisseur of cheap popcorn carefully counted 773 kernels and put them in a popper. After popping, the unpopped kernels were counted. There were 86. (a) Construct a ...

(A) 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: 0 260 356

Confidence Interval

A manufacturer would like to estimate the average number of copies that can be made from a single bottle of toner. A random sample of 20 bottles was selected for this experiment. For the 20 bottles of toner the average number of pages was 1535 with a standard deviation of 50 pages. a) Compute the 95% confidence interval f

Confidence interval samples

A sample of n=16 scores is obtained from an unknown population. The sample has a mean of M=46 with SS=6000. a. Use the sample data to make an 80% confidence interval estimate of the unknown population mean. b. Make a 90% confidence interval estimate of μ. c. Make a 95% confidence interval estimate of μ.

Finding a confidence Interval

Use the given confidence level and sample data to find a confidence interval for estimating the population mean m 1. salaries of college graduates who took a statistics course in college : 95% confidence; n=41, x(bar over x) = $67,200, and o( omega or sigma )is known to be $18, 277.