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Confidence Interval

Statistics: Margin of Error, Sample Sizes and Confidence Intervals

Question: Give an estimate of the sample size needed to obtain the specified margin of error for a 95% confidence interval. Margin of error = 0.01, standard deviation = 0.25 Scenario: Researchers want to determine the mean number of hours students spend watching TV. A margin of error of 0.25 hour is desired. Past studies

Normal Distribution, Sampling distribution, Confidence interval

1) The distribution of sample mean for samples of 500 homes is normal with a mean of 2.64 and a standard deviation of 0.06. Suppose you select a random sample of n=500 homes and determine that the mean number of people per home for this sample id 2.55. How many standard deviations is the sample mean of the sampling distribution?

Basic Business Statistics: 17 Multiple choice questions on Sampling distribution, Normal Distribution, t-distribution, confidence interval estimate, standard error of the mean, finite population correction factor, sample size, degrees of freedom, one-sided confidence interval estimate

Please see attached. 1. For air travelers, one of the biggest complaints is of the waiting time between when the airplane taxis away from the terminal until the flight takes off. This waiting time is known to have a skewed-right distribution with a mean of 10 minutes and a standard deviation of 8 minutes. Suppose 100 flights ha

Statistics : Confidence Interval and Z-Statistic

In the spring of 2002, residents of the United States were quite worried about the possibility of further terrorists attacks. To gauge the public's sentiment on this topic, the Gallup Poll asked 1002 U.S. adults the following question during May 20-22, 2002. How likely is it that there will be further acts of terrorism in the

Proportions and Confidence Interval

1) Does the M&M/Mars Corporation use the same proportion of red candies in its plain and peanut varieties? A random sample of 56 plains M&Ms contained 12 red candies, and another random sample of 32 peanut M&Ms contained 8 red candies. a) Construct a 95% confidence interval for the difference in the proportions of red candies f

Point Estimate, Margin of Error and Confidence Interval

1) In an attempt to compare the starting salaries of college graduates majoring in education and social sciences, random samples of 50 recent college graduates in each major were selected and the attached information was obtained. (see attachment for data table) a) Find a point estimate for the difference in the average sta

Margin of error and statistical testing

Question: Do you have university education? Yes=45% (n=450) No=60% (n=800) To find out whether 45% is significantly different from 60%, I use this: =SQRT (45*(100-45)*1.96*1.96/450) answer=4.59 Then I use =SQRT(+60*(100-60)*1.96*1.96/800) answer=3.40 Then I calculate the total margin of error

Confidence Interval; Sampling Distribution; Mean and Standard Deviation

1. A parcel service randomly selected 48 packages it received. The sample has a mean weight of 18.6 pounds. Assume that σ = 3.4 pounds. Construct a 90% confidence interval for the true mean weight, μ, of all packages received by the parcel service. 2. A phone company wants to estimate the mean duration of local

P-Values, Null Hypotheses and Confidence Intervals

I have some trouble understanding the concept first and it will be really helpful if I can see the problem worked out. Here is example question from the textbook. Please help me. The data studies the effect of dietary calcium on blood pressure. In the experiment, one group of black male adults received calcium supplements f

Confidence Intervals and Hypothesis Test.

The mean and standard deviation of the sample of 65 customer satisfaction ratings are x-bar = 42.95 and s = 2.6424. If we let "mu" denote the mean of all possible customer satisfaction ratings: a) Calculate 95 and 99 percent confidence intervals for "mu". b) Using the 95 percent confidence interval, can we be 95% confident

Sample Mean / Mean of Population

Vito has completed the analysis of some sample data from a recent survey of local high school students. He has determined that his sample has attended an average of 145 days of school this year, with a standard error of the average of 8 days. The sample was random and fairly large. (refer to document attached for other given inf

If you promised to deliver a survey that is accurate plus minus 5% at a confidence level of 90%, can you say, using a conservative basis for estimation, that you have reached your objective?

Having been retained by the National Native American Political Party to conduct a poll of residents of Muscogee, Oklahoma, you have worked diligently on completing interviews with residents of that town for three weeks. Your budget of $10,000 is expended. You have completed 270 interviews. (A) If you promised to deliver a su

Confidence Intervals

Decoders often use the fact that the letter "e" appears in written work more than any other letter. Make a photocopy of an article in a newspaper or magazine {see article below}. Choose two different paragraphs from that article/page (must be a minimum of 25 words in each paragraph and the paragraphs must contain the letters e a

Confidence Intervals

Suppose an SRS of 25,000 Americans were surveyed and 16,000 of them said they have blue colored eyes. a) Create a 98% confidence interval estimator for the population proportion of Americans that have blue colored eyes. b) What is the minimum sample size that would be required to estimate the population's proportion to wi

Confidence Intervals

To estimate the mean size of maple trees in a certain area of the Adirondacks. A sample of 15 maple tree heights is collected (refer to the data set). Data Sheet numbers: 50, 41, 31, 33, 47, 39, 41, 44, 39, 32, 35, 43, 37, 49, 51 a) Determine a 90% confidence interval for the population mean of maple tree heights.

Confidence Intervals

8.20 425 510 629 236 654 200 276 501 811 332 424 674 676 694 710 662 633 a. Find a 90% confidence interval for the mean number of tongue flicks per 20 minutes for all juvenile common lizards. Assume a population standard deviation of 190.0 (note: The sum of the data is 9047.) b. interpret your answer from part (a)

Normal Distribution, Mean and Standard Deviation

7.40 A variable of a population has a mean of m = 35 and a standard deviation of o = 42. a. If the variable is normally distributed, identify the sampling distribution of the sample for samples of 9. b. Can you answer part (a) if the distribution of the variable under consideration is unknown? Explain your answer. c. C

Test of hypothesis, Confidence Interval

1) Recruit 25 volunteers who have recieved a medication and find they have a mean concentration of 7 with a standard deviation of 2. Assume normall ditributed. FIND: 95% CONFIDENCE INTERVAL for pop mean concentration Find: 99% confidence interval for pop var of conc HOW large a sample os needed to ensure the length of the

Confidence Intervals

In the atmosphere, the ratio of toxic gas, for a given volume of air, is a normally distributed random variable with mean μ and variance σ² which are unknown. We take n samples, whose values are X1, X2,..., Xn. Please see attachment for questions 1, 2, and 3.

Confidence Intervals, Samples, and Unknown Variance

Let (X1, X2,..., Xn) be a sample, where each Xi is a random variable of normal distribution with mean mu and variance sigma². Let us suppose that n = 20, and sigma² = 9. An experiment has yielded the results (X1, X2,..., X20), and we have calculated that the empirical mean x20 = 2.09. 1) Give a confidence interval with leve

Probability Confidence Intervals

I am currently studying probability and am having a bit of trouble with the following questions. Can you help me? If you can, thank you very much. The questions are: 1.) An office manager wishes to estimate the mean time required to handle customer complaints. A sample of 38 complaints shows a mean time of 28.7 minutes with a

Confidence interval for the true population proportion

A citizen's group is interested in the portion of the population that opposes the expansion at O'Hare airport. In a survey of 1,440 randomly selected people, 1098 people opposed the expansion. Construct a 95% confidence interval for the true population proportion.