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Confidence Interval

Constructing Confidence Interval Estimates

1. In his management information systems textbook, Professor David Kroenke raises an interesting point: "If 98% of our market has Internet access, do we have a responsibility to provide non-Internet materials to that other 2%? Suppose that 98% of the customers in your market do have Internet access, and you select a random sa

95% confidence interval estimate

Error -0.002 0.0005 0.0025 0.001 0.002 0.001 0.005 -0.002 0 0.001 -0.0025 -0.003 0.001 -0.0005 0 -0.003 -0.001 0.0005 0.0025 -0.0025 0.002 0.001 0.001 0.001 -0.002 -0.003 -0.0015 -0.0005 0 -0.0025 -0.003 -0.001 0.002 -0.001 0 0.003 0.0015 0 0 -0.0025 0.0005 0.001 0.0005 0.001 0.0025

Confidence Interval Estimates

1. One operation of a mill is to cut pieces of steel into parts that are used in the frame for front seats in an automobile. The steel is cut with a diamond saw, and the resulting parts must be cut to be within +/- 0.005 inch of the length specified by the automobile company. The measurement reported from a sample of 100 steel p

Comparing Confidence Intervals

1. The eruption height and the time interval after eruption of a geyser were measured and are shown below. Height (x) 107 145 123 120 127 124 138 150 Interval after (y) 62 84 73 66 78 67 80 83 a. Find the value of the linear correlation coefficient r. r= _____ (roun

Margin of Error and Corresponding Confidence Levels

1. Assume that a randm sample is used to estimate a popultion proportion p. Find the margin of error E that corresponds to the given statistics and confidence level. 98% confidence; the sample size is 1206, of which 35% are successes The margin of error E= ______ (round to four decimal places as needed) 2. Use the give

Statistics: Tweens, Rainfall, Body Temperature

Exercise 1 When it comes to advertising, "'tweens" are not ready for the hard line messages that advertisers often use to reach teenagers. The Geppeto Group study found that 78% of 'tweens understand and enjoy ads that are silly in nature. Suppose that the study involved n = 1030 'tweens. a. Construct a 90% confidence interval

Estimates and sample sizes

The administration of a large university wants to estimate what proportion of their full time engineering students are female. If she obtains a random sample of a 100 engineering students from the day campus of which 30 students are female what would her confidence interval be if she needs a confidence level of 95%? a. Wha

Estimate and Sample Sizes

I. In a study designed to test the effectiveness of acupuncture for treating migraine headaches 36 subjects were treated with acupuncture and 25 subjects were given a sham treatment. The number of migraine attacks for the acupuncture group had a mean of 2.609 and a sample deviation of 1.8. Construct a 95% confidence interval

Confidence Intervals: Time Watching TV

The sponsors of television shows targeted at the children's market wanted to know the amount of time children spend watching TV, since the types and number of programs and commercials are greatly depended on this information. As a result, a survey of 100 children was conducted to estimate the average number of hours children spe

Comparisons Between Confidence Interval Estimates

The overall miles per gallon (MPG) of 2009 Sedans priced under $20,000. 27 31 30 28 27 24 29 32 32 27 26 26 25 26 25 24 (a) Construct a 95% confidence interval estimate for the population mean MPG of 2009 Sedans (4 cylinder) priced under $20,000, assuming normal distribution. (b) Interpret the interval constructed in (a).

Statistics: 95% Confidence Intervals

1. The recommended retail price of a popular new midsize SUV is $30,985. The price of the SUV in a sample of 30 deaerships in on average $27,895 with a standard deviation of $1,150. If this is a random sample and the price can be assumed to be normally distributed, construct a 95% confidence interval of the average sale price

Confidence Intervals and Prediction Intervals

See the data in the attached file and answer the following questions. Question 1 Construct a 95% confidence interval for an average value of y given that x = 4. Remember the format is (x.xx, x.xx) Question 2 Construct a 95% prediction interval for y given that x = 4.

Determining Confidence Intervals

In a recent study of 86 working adults, the mean number of hours per week spent talking on the phone was 21.6. The sd= 5.7 hours. Calculate the 90% confidence level for the mean. The format for writing a confidence interval is (xx.x, xx.x)

Confidence Intervals and Population Means

Construct a 95% confidence interval to estimate the population mean with a sample mean = 110 and ? = 30 for the following sample sizes: a) n = 30 b) n = 45 Please write confidence interval in parentheses with the lower confidence limit first, followed by the upper limit, separated by a comma.

Confidence Intervals in Excel

Can you put this on excel for me? I attempted several times and I can't figure out where I'm going wrong. My example is not related to my particular business, company, or industry, however being an annual pass holder to the Walt Disney World parks, the first thing that came to mind when reading the question(s) was an example

Confidence Intervals and Interval Estimates

"A confidence interval is an interval estimate around a sample mean that provides us with a range [within which] the true population mean lies" "The purpose of generating a confidence interval is to provide an estimate for the value of the population mean" Identify a business situation where you might want to make an est

Statistics: Confidence Interval for Population Proportion

In a Gallup Poll of 1005 randomly selected Americans in April 2006, 482 responded "yes" to the question, "Do you consider the amount of federal income tax you have to pay as too high?" a. If appropriate, find a 90% confidence interval for the population proportion of all Americans who consider that the amount of federal inco

Statistics: Confidence Intervals T-Interval Mean

A 2007 study reported in Science magazine stated that fifth-grade teachers scored a mean of 3.4 (out of 7) points for "providing evaluative feedback to students on their work." Assume that the sample size was 36 and the sample standard deviation was 1.5. a. Find T(alpha/2) for a confidence interval with 90% confidence. b. Co

Evalutating Confidence Intervals

The Statistical Abstract of the United States reports that the mean daily number of shares traded on the NYSE in 2002 was 1441 million. Assume that the population standard deviation equals 500 million shares. Suppose that, in a random sample of 36 days from the present year, the mean daily number of shares traded equals 1.5 bill

Shell Lengths of Loggerhead Sea Turtles

Shell Lengths of Loggerhead Sea Turtles The National Marine Fisheries Services is part of the National Oceanic and Atmospheric Administration. NMFS's programs support the conservation and management of living marine resources. There are six species of sea turtles in the United States and all are prote

Calculating Confidence Intervals and Proportion

Problem 4.1: Given the data set body-weight.sav, use SPSS to calculate the 90%, 95% and 99% confidence intervals for the mean of the variable weight. Interpret the three confidence intervals in terms of whether there is a significant difference between the mean of the sample and a hypothesized mean of 150. Problem 4.2: Every

Proportion of Adults Planning on Buying a New Car

A marketing research firm wishes to estimate the proportion of adults who are planning to buy a new car in the next 6 months. A simple random sample of 100 adults led to 22 who were planning to buy a new car in the next 6 months. a. Compute the 95% confidence interval for the proportion of adults who are planning to buy a ne

Sampling Distribution and Confidence Intervals

7.11 A simple random sample of n = 300 full-time employees is selected from a company list containing the names of all, N = 5,000 full-time employees in order to evaluate job satisfaction. a. Give an example of possible coverage error. b. Give an example of possible nonresponse error. c. Give an example of possible samplin

Type 2 Error

1. In random samples of 25 from each of two normal populations, we found the following statistics: x1 bar = 524 s1 = 129 x2 bar = 469 s2 = 131 a) estimate the difference between the two population means with 95% confidence. b) repeat part a) increasing the standard deviations of s 1 to 255 and s 2 to 260. c) describe what h

Statistics Problem Set: Coffee or Tea?

1. Poll of 200 people was conducted to analyze if liking Tea or Coffee is related to gender. Here are results of this poll: Tea Coffee Male 10 70 Female 40 80 a) Based on these data, what is the probability that a person likes Coffee if the person is a Male?

Statistics Problem Set: Developing Confidence Intervals

1. A car rental office checks out an average of 30 cars per day with a standard deviation of 8 cars. If a sample of 25 days of operation is selected and the sample mean is computed. What is the value for the standard error of the mean? What is the probability that the sample mean for the 25 days will be within 27 and 32 cars?

Proportion and and Confidence Intervals

a. In your sample, what is the proportion of males who have brown ("Brown" only) eyes? 3 of 8 males have brown eyes. (.375) b. What is a 95% confidence interval on the proportion of males with brown eyes in the "population" (The population here is of all men.) c. In your sample, what is the proportion of females who ha

Weibull Distribution: Sample Items in a Test Configuration

A sample of 1000 items was placed in a test configuration such that all were operating under load. The data in the attachment contains the number still running at the end of each day for 90 days. a. Estimate the parameters of a Weibull failure time distribution. b. Construct 90% confidence interval for those parameters. c.

Probability, Test Statistics and Error

In a recent year, scores on a standardized test for high schools student with a 3.50 to 4.00 grade point average were normally distributed, with a mean of 37.9 and a standard deviation of 2.4. A student with a 3.50 to 4.00 grade point average who took the standardized test is randomly selected. Four Decimal Places for Questi

The Quick Method

The Quick Method: The quick method uses "p-hat +/- (1/?n)" as a rough recipe for a 95% confidence interval for a population proportion. The margin of error from the quick method is a bit larger than needed. It differs most from the more accurate method when p-hat is close to 0 or 1. An SRS of 500 motorcycle registrations finds t