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Confidence Interval

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

Confidence intervals for the population mean

The owner of Britten's Egg Farm wants to estimate the mean number of eggs laid per chicken. A sample of 18 chickens shows they laid an average of 25 eggs per month with a standard deviation of 7 eggs per month. (a-1) What is the value of the population mean? It is unknown. 25 7 (a-2) What is the best e

Margin of Error Calculations

1. The width of a confidence interval is always twice what value? 2. Suppose = 29:47 and x = 26:54. What is the sampling error? 3. Let c = 0:99, s = 5:6, and n = 87. What is the margin of error, E? 4. Construct the confidence interval for the population mean, . c = 0:90, x = 58:62, s = 1:84, and n = 65. Use the confidenc

Statistics and Confidence Intervals Deviations

Work on an Excel spreadsheet with results linked to data using Excel functions and cell addresses. To derive the confidence intervals for the mean with known standard deviation, use the z table from Table E.2 or =normsinv. 1) The Harvard class of 2009 had a reunion attended by 36 members. It was determined that they had mar

Probability Problem Set

Problem 3 a. A random sample of 25 was drawn from a normal distribution with a standard deviation of 5. The sample mean is 80. Determine the 95% confidence interval estimate of the population mean. b. Repeat part (a) with a sample size of 100. c. Repeat part (a) with a sample size of 400. d. Describe what happens to the conf

Two questions related to constructing confidence intervals.

A sample of 144 cans of coffee showed an average weight of 16 ounces. The standard deviation of the population is known to be 1.4 ounces. a. Construct a 68.26% confidence interval for the mean of the population. b. Construct a 97% confidence interval for the mean of the population.

Value sample and interval

I am having problems with these sample problems. Can you please help me? I have attached the following questions within an excel sheet for your usage in deriving the solutions. A 90 % confidence interval for a situation is developed and is given by the following 48 < µ < 64. a) Give the value of the sample mean that was us

Statistics Review Questions.

Choose the best answer to the following questions. 1. (TCO 9) The hours of study and the final exam grades have this type of relationship: ? = 7.35(hours) + 34.62. Based on this linear regression equation, estimate the expected grade for a student spending 8 hours studying. Round your answer to two decimal places.

Confidence interval containing the...

Which is the best and why? A confidence interval (CI) is a range of scores with specific boundaries that should contain the ______ mean. A. sample B. population C. standard error D. none of the above

Statistics Problem Set: USGA Golf Ball Test

5.70 USGA golf ball test. The United States Golf Association USGA tests al new brands of golf balls to ensure that they meet USGA specifications. One test conducted is intended to measure the average distance traveled when the ball is hit by a machine call "Iron Byron" a name inspired by the swing of the famous golfer Byron Nels

Statistics Problem Set: Scanning Errors at Wal-Mart

5.60 It costs you $10 to draw a sample of siz n = 1 and measure the attribute of interest. You have a budget of $1,500. a. Do you have sufficient funds to estimate the population mean for the attribute of interest with a 95% confidence interval 5 units in width? Assume sigma = 14. b. If you used a 90% confidence level, would

Statistics Problem Set: Intervals

5.2. What is the confidence level of each of the following confidence intervals for the mean? (see attached). 5.20. The "Raid" test kitchen. According to scientists, the cockroach has had 300 million years to develop a resistance to destruction. In a study conducted by researchers for S.C. Johnson & Son, Inc. (manufacturers o

Hypothesis Testing and Confidence Intervals with Minitab

Your manager has speculated the following: a. the average (mean) annual income was less than $50,000, b. the true population proportion of customers who live in an urban area exceeds 40%, c. the average (mean) number of years lived in the current home is less than 13 years, d. the average (mean) credit balance

Confidence Interval Estimate, Hypotheses and Test Statistics

1. Mimi was the 5th seed in 2012 UMUC Tennis Open that took place in August. In this tournament, she won 83 of her 100 serving games. Based on UMUC Sports Network, she wins 80% of the serving games in her 5-year tennis career. (a) Find a 95% confidence interval estimate of the proportion of serving games Mimi won. (Show wor

Null Hypothesis and Confidence Interval

Please see the attachment for the fully formatted solution. The Osborne manufacture makes a soft drink dispensing machine that allows customers to get soft drinks from the machine in a cup with ice. When the machine is running properly, the average number of fluid ounces in the cup should be 14. Periodically the machines need

Statistics Coefficient Importance

DQ 1 If we wish to have a 95% confidence interval, what would be the value of the confidence coefficient? [Hint: Table 4B] DQ 2 In your own words, describe the relationship between the standard error (of the mean) and maximum error. The standard error is the standard deviation. The maximum error is the product of the s

Confidence Intervals of Population Mean

According to a report produced by the New South Wales Ministry of Health, 46% of hospitalisations occur in people aged sixty years and over (60+). You randomly select forty people who were hospitalized in the past year and find that fifteen of them are 60+. a) Perform a hypothesis test at the 5% level of significance that 46

Statistics and Confidence Intervals

John Kim is the purchasing manager for your computer, Inc., a manufacture of network servers. A truckload of sheet metal has just arrived. Previous experience with the supplier suggests that the thickness of the sheet metal follows a normal distribution. A random sample of 23 sheets yields an average thickness of 0.192 inches

Sample Size and Confidence Intervals in Statistical Analysis

If a random sample of 10 people found that 9 were pro-life (i.e., 90%), while another random sample of 1000 people from the same population found that 550 were pro-life (i.e. 55%), which would you find to be more significant? Why? When pollsters report results of a poll, they often include the margin of error but not much m