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# Confidence Interval

### Statistics - Multiple Choice Questions

See attached file for full problem description. 1. The standard normal distribution a. is a special case of the normal distribution b. has a mean equal to 0 and a standard deviation equal to 1 c. measures the distance from the mean in units of the standard deviation d. all of the above 2. Any normal distribution

### Students t test with Confidence Intervals

Body mass index is calculated by dividing a person?s weight by the square of his or her height; it is a measure of the extent to which the individual is overweight. For the population of middle-aged men who later developed diabetes mellitus, the distribution of baseline body mass indices is approximately normal with unknown mean

### Confidence Interval

In order to compare the means of two populations, independent random samples of 400 observations are selected from each population, with the following results: Sample 1: xbar = 5,275 s= 150 Sample 2: xbar = 5,240 s= 200 a. Use a 95% confidence interval to estimate the difference between the population means (?1 - ?2 ).

### Task: Estimation and Confidence Intervals

A processor of carrots cuts the green top off each carrot, washes the carrots, and inserts six to a package. Twenty packages are inserted in a box for shipment. To test the weight of the boxes, a few were checked. The mean weight was 20.4 pounds, the standard deviation was 0.5 pounds. How many boxes must the processor sample to

### Estimation and Confidence Intervals for American Sugar Producers Association

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. 1. What is the value of the population mean? What is the best estimate of this value? 2. Explain why we need to use t

### Constructing a confidence interval for mean age

Constructing a confidence interval - The stemplot below lists the ages of applicants who were successful in winning promotion (based on data from "debating the use of statistical evidence in allegations of age discrimination," by barry and boland, American Statistician, vol 58 no. 2). Assume that the sample is a simple random sa

### Testing of hypothesis and 95% Confidence interval

According to a survey conducted in October, 2001, consumers were trying to reduce their credit card debt (Margaret Price, "Credit Debts Get Cut Down to Size," Newsday, November 25, 2001, F3). Based on a sample of 1,000 consumers in October 2001 and in October 2000, the mean credit card debt was \$2,411 in October 2001 as compare

### One-Sample Hypothesis Test Confidence Intervals

One-Sample Hypothesis Test Confidence Intervals Take a random sample and perform a t-test against a population mean (no time series for any parts of this project.) Test a hypothesis about a population mean. Besides the instructions above, explain what assumptions you made. Note: n must be between 15 to 20! Use no other sample

### Constructing Confidence Intervals for mean weight

Listed below are weights (in grams) from a sample of bats. Construct a 95% confidence interval estimate of their mean weight. Are the confidence interval limits very different from the limits of 1.56 and 1.87 that are found when assuming that σ is known to be 0.30g ? 1.7 1.6 1.5 2.0 2.3 1.6 1.6 1.8 1.5

### Estimating a Population Proportion for Medical Malpractice Data

Medical Malpractice - An important issue facing Americans is the large number of medical malpractice lawsuits and the expenses that they generate. In a study of 1228 randomly selected medical malpractice lawsuits, it is found the 856 of them were later dropped or dismissed (based on data from the physician insures association of

### Compute a 95% confidence interval for the proportion of all depressed individuals taking the drug who find relief

A researcher wants to estimate the proportion of depressed individuals taking a new anti-depressant drug who find relief. A random sample of 275 individuals who had been taking the drug is questioned; 222 of them found relief from depression. Based upon this, compute a 95% confidence interval for the proportion of all depressed

### What is the lower/upper limit of the confidence interval?

A corporation that maintains a large fleet of company cars for the use of its sales staff is interested in the mean distance driven monthly per sales person. The following table gives the monthly distances in miles driven by a random sample of sales persons: 17 sales persons: 2522, 2535, 2305, 1946, 2185, 2219, 1873, 1936, 1

### Inferences based on two samples

Refer to the data for 308 diamonds saved in the diamonds file. Two quantitative variables in the data set are number of carats and selling price. One of the qualitative variables is the independent certification body that assessed each of the stones. Three certification bodies were used: GIA, IGI, and HRD. The MINITAB print

### Lower/Upper Limits of 90% Confidence Interval

Suppose that 240 out of a random sample of 325 letters mailed were delivered the day after they were mailed. Based on this compute a 90% confidence interval for the proportion of all letters mailed that were delivered the day after they were mailed. Then answer the following. A. What is the lower limit of the 90% confidence

### Probability - Confidence Interval for Population Proportion

Question: From a population of 1600 documents a random sample of 100 documents is drawn and found 10 defects in the sample. Find the representative number of defects in the total population of 1600 documents at 80% confidence level, at 90% confidence level and at 95% confidence level. Please see the question file attached.

### The U.S. Department of Transportation defines an airline flight as being "on-time" if it landed less than 15 minutes after the scheduled time shown in the carrier's Computerized Reservation System.

The U.S. Department of Transportation defines an airline flight as being "on-time" if it landed less than 15 minutes after the scheduled time shown in the carrier's Computerized Reservation System. Cancelled and diverted flights are counted as late. A study of the 10 largest U.S. domestic airlines found Southwest Airlines to h

### Confidence Interval for Difference

12. Suppose that A is the curing method that is commonly used and that B and C are new curing methods developed by the engineer. A 95% confidence interval for l = muA - (1/2)(muB + muC) is: (see attachment for multiple choice solutions) On number 12, how can we get +- 0.941? The standard deviation is 1.865, right?? Th

### What is the degree of confidence? Find the margin of error.

(1) The confidence interval: 5.06 < sigma2 < 23.33 is for the population variance based on the following sample statistics: n = 25, x-bar = 41.2, and s = 3.1 What is the degree of confidence? Use only integers, no % sign and no decimal places. (2) Find the margin of error. 95% c

### Confidence interval for proportions

In a city of 50,000, you conducted 1,000 interviews on a random sample basis to find out how many respondents wore sneakers. Of the 1,000 interviewed, 300 wore sneakers. With a 95% confidence, how precise is your estimate?

### Sample Size, Margin of Error, Confidence Level

Sample Size, Margin of Error, Confidence Level. See attached file for full problem description.

### Statistics - Multiple Choice: estimation, z value, confidence interval, t statistic, point estimate for population proportion, error of the estimation, point estimate of the population variance, chi-square values, sample size

Question 1: When a statistic calculated from sample data is used to estimate a population parameter, it is called : an interval estimate a point estimate a statistical parameter a good guess Question 2: A large appliance company sends out technicians to unpack, assemble, and connect every gas dryer that is sold. I

### Margin of error, Confidence interval estimate, Sample size, Point Estimate

Attached please find four Statistics problems. Please answer each question in detail, showing all intermediate steps as well as the final resolution. Problem #4 Fortune Survey A survey of small businesses with Web sites found that the average amount spent on a site was \$11,500 per year (Fortune, March 5, 2001). Given a

### 95% confidence interval for the population proportion, sample without replacement

1. Ophelia O'Brien, VP of Consumer Credit of American First Banks (AFB), has implemented a 'fast feedback' to keep her informed of the default rate on personal loans at the AFB member banks. On each Friday, the default rate is calculated for a sample of 500 personal loans. Last Friday's sample contained 30 defaulted loans. The 9

### Point estimate and confidence interval of mean

The manufacturer of a new line of ink jet printers would like to include as part of their advertising the number of pages a user can expect from a print cartridge. A sample of 10 cartridges revealed the following number of pages printed. 2,698 2,028 2,474 2,395 2,372 2,475 1,927 3,006 2,334 2,379 a. What is the po

### Develop a 98 percent confidence interval for the population mean.

An important factor in selling a residential property is the number of people who look through the home. A sample of 15 homes recently sold in the Buffalo, New York, area revealed the mean number looking through each home was 24 and the standard deviation of the sample was 5 people. Develop a 98 percent confidence interval for t

### Estimators and Confidence Interval

A certain medication is known to increase the pulse rate of its users. The standard deviation of the pulse rate is know to be 4 beats per minute. A sample of 40 users had an average pulse rate of 98 beats per minute. Find the 95% confidence interval of the true mean (of the population)? Give at least 2 properties of a good es

### Sample size estimation and Confidence Interval

1. A student surveys 100 classmates by asking each if they have outstanding loans. After finding the sample of proportion for this sample of n = 100 subjects, can the methods of this section be used to estimate the proportion of all adults who have outstanding loans? Why or why not? 2. Express the confidence interval 0.600 < p

### Use Statdisk to find the following confidence interval estimates of the percentage of yellow peas.

1. Mendelian Genetics?When Mendel conducted his famous genetics experiments with peas, one sample of offspring consisted of 428 green peas and 152 yellow peas. a. Use statdisk to find the following confidence interval estimates of the percentage of yellow peas. 99% confidence interval_______________ 98% confidence interval___

### Survey Data and Information in the Media

How much does understanding the concept of confidence interval affect the way you draw conclusions from survey data or information presented in the news or media?

### Using Confidence Intervals and Hypothesis Testing

See attached file for full problem description. Confidence Intervals 1. For a sample mean of 4 and a population standard deviation of 0.3 with a sample size of 100, find the 95% CI for the population mean. 2. Using Internet Explorer, go to http://www.rossmanchance.com/applets/Confsim/Confsim.html . (It may take a minut