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# Confidence Interval

### Statistics 95% confidence interval to population proportion. Difference in means

Question (1) The policy of the Suburban Transit Authority is to add a bus route if more than 55 percent of the potential commuters indicate they would use the particular route. A sample of 70 commuters revealed that 42 would use a proposed route from Bowman Park to the down-town area. Does the Bowman-to-downtown route meet th

### Multiple Choice

1. Compare the results of the large sample with the results from the small sample and explain what they mean. a. As the sample size gets larger, the interval decreases. We become more confident that the mean will lie in our interval. b. As the sample gets larger, the interval increases. We become more confident that the mean

### Confidence Interval and Hypothesis testing

In our bakery, a sample of 60 loaves of bread is found to have a mean weight of 35 ounces with a standard deviation of 1.21 ounces. a. Using the sample, determine a 98% confidence interval for the mean weight of the entire daily output. b. Determine how large a sample should be taken to be 90% confident that the sample mean i

### 4 Stats Questions

1. The business college computing center wants to determine the proportion of business students who have personal computers at home. If the proportion exceeds 30%, then the lab will scale back a proposed enlargement of its facilities. Suppose 250 business students were randomly sampled and 75 have pcs at home. Find the rejection

### Statistics Problem Set

1. To help consumers assess the risks they are taking, the food and drug administration publishes the amount of nicotine found in all commercial brands of cigarettes. A new cigarette has recently been marketed. The FDA tests on this cigarette gave a mean nicotine of content 28.2 milligrams and standard deviation of 2.7 milligram

### A roper starch survey

A roper starch survey asked employees ages 18 to 29 whether they would prefer better health insurance or a raise salary (USA Today, September 5, 200). Answer the following questions assuming 340 of 500 employees said they would prefer better health insurance over a raise. a) what is the point estimate of the proportion of emp

### Confidence interval estimation of population proportion. ..

A roper starch survey asked employees ages 18 to 29 whether they would prefer better health insurance or a raise salary (USA Today, September 5, 200). Answer the following questions assuming 340 of 500 employees said they would prefer better health insurance over a raise. a) What is the point estimate of the proportion of emp

### Point Estimation and Interval estimation

47) Arthur D. Little, Inc. estimates that approximately 70% of mail received by a household is advertisements (Time, July 14, 1997). A sample of 20 households shows the following data for the number of advertisements received and the total number of pieces of mail received during one week. a) What is the point estimate of the

### Department store chain, confidence interval for mean

1. A major department store chain is interested in estimating the average amount its credit card customers spent on their first visit to the chain's new store in the mall. Fifteen credit card accounts were randomly sampled and analyzed with the following results: &#935; = \$50.50 and s2 = 400. Assuming the distribution of th

### What is the lower/upper limit of 90% confidence interval?

The lifetime of a certain brand of battery is known to have a standard deviation of hours. Suppose that a random sample of such batteries has a mean lifetime of hours. Based on this sample, find a confidence interval for the true mean lifetime of all batteries of this brand. Then complete the table below. Carry your inte

### To find the confidence interval of difference of mean

Construct a 90% confidence interval for mu sub d, the mean of the differences d for the population of paired data. Assume that the population of paired differences is normally distributed. d-bar = 3.125; s d = 2.911; n = 8 2.435 < <MUµd < 3.815 1.175 < µd < 5.075 2.435 < µd < 5.075

### Calculating the Margin of Error

Use the confidence level and sample data to find the margin of error. Systolic blood pressure for women ages 18-24: 94% confidence; n = 81, x-bar = 113.8 mm Hg, sigma = 12.8 mm Hg Round to the nearest one decimal place. 2.7 mm Hg 2.6 mm Hg 42.6 mm Hg 9.0 mm Hg

### Confidence interval for paired data

Construct a confidence interval. See attached file for full problem description.

### Teenage Drinking and Sexual Activity Statistics

I. Of kids who do not drink alcohol, 137 are sexually active and 3,295 are not ii. Of kids who sometimes drink alcohol, 78 are sexually active and 557 are not. A. (5) Construct a 95% confidence interval for the proportion of non-drinking kids that are sexually active. B. (5) What is the odds ratio of sexual activity for dri

### Confidence interval and testing of hypothesis problems

1. A manufacturer of small appliances employs a market research firm to estimate retail sales of its products by gathering information from a sample of retail stores. This month an SRS of 75 stores in the Midwest sales region finds that these stores sold an average of 24 of the manufacturer's hand mixers, with standard deviatio

### Sample size

You are to conduct a sample survey to determine the mean family income in a rural area of central Florida. The question is, how many families should be sampled? In a pilot sample of 10 families, the standard deviation of the sample was \$500. The sponsor of the survey wants you to use the 95% confidence interval. The estimate is

### Confidence Interval

Dr. Patton is a professor of English. Recently, he counted the number of misspelled words in a group of student essays. For his class of 40 students, the mean number of misspelled words was 6.05 and the standard deviation 2.44 per essay. Construct a 95% confidence interval for the mean number of misspelled words in the populatio

### Confidence level - margin of error

Use the confidence level and sample data to find the margin of error E. Weights of eggs: 95% confidence; n = 49, x-bar = 1.70 oz, sigma = 0.33 oz

### Confidence interval construction population proportion

Use the given degree of confidence and sample data to construct a confidence interval for the population proportion p: n = 60, x = 19, 95 percent.

### Confidence interval for a population mean

A researcher wishes to construct a 95% confidence interval for a population mean. She selects a simple random sample of size n=20 from the population. The population is normally distributed and sigma is unknown. When constructing the confidence interval, the researcher should use the t distribution; however, she incorrectly uses

### Confidence level and sample data

Use the confidence level and sample data to find a confidence interval for estimating the population mean m. Test scores: n = 101, x-bar = 96.8, sigma = 8.3, 99 percent confidence

### Calculating p-hat from confidence interval

The following confidence interval is obtained for a population proportion, p:(0.458, 0.490). Use these confidence interval limits to find the point estimate, p-hat.

### Estimated proportion defective, 95% confidence interval

Schadek Silkscreen Printing, Inc. purchases plastic cups on which to print logos for sporting events, proms, birthdays, and other special occasions. Zack Schadek, the owner, received a large shipment this morning. To ensure the quality of the shipment, he selected a random sample of 300 cups. He found 15 to be defective. a.

### A recent survey of 32 unemployed male executives showed that it took an average of 20 weeks for them to find another position

A recent survey of 32 unemployed male executives showed that it took an average of 20 weeks for them to find another position. The standard deviation of the sample was 6.2 weeks. Construct a 95 percent confidence interval for the population mean. Is it reasonable that the population mean is 26 weeks?Justify your answer.

### Students t-test and confidence intervals for insurance carriers data.

The data that you will be using for this exercise came from a survey of two insurance carriers. The first carrier (C1) was compared against the second competitor (C2). The insurance company management team wants to know how Carrier 1 compared to the second carrier. Data from 160 respondents are contained in the Excel spreadshe

### Probability and Statistics

1. TFQ: Amy wants to find a 96% confidence interval for the amount of time it takes to get to work. She kept records for 35 days and found her average time to commute to work was 20.5 minutes with a standard deviation of 3.6 minutes. Amy's maximum error of estimate would be 1.25 minutes. 2. TFQ: Charles wants to be 90% c

### Drawing Inference from Large Samples

I need some details on how the answer was obtained: Computing from a large sample, one finds the 95% confidence interval for the mean to be {6.8, 14.2}. Based on this information alone, determine the 90% confidence interval for the mean.

### STATISTICS HELP NEEDED

Question 1: Find the number of successes x suggested by the given statement. Among 680 adults selected randomly from among the residents of one town, 27.2% said that they favor stronger gun-control laws. a. 183 b. 184 c. 186 d. 185 Solve the problem. In a game, you have a 1/29 probabilit

### Construction of confidence interval for mean and population proportion.

* Construct the indicated confidence interval for the difference between population proportions p1 - p2. Assume that the samples are independent and that they have been randomly selected. x1 = 57, n1 = 95 and x2 = 84, n2 = 96; Construct a 98% confidence interval for the difference between population proportions p1 - p2. ....

### Estimation: Confidence Intervals and Sample Size

1) In a poll to estimate presidential popularity, each person in a random sample of 1,000 voters was asked to agree with one of the following statements: 1. The President is doing a good job. 2. The President is doing a poor job. 3. I have no opinion. A total of 560 respondents selected the first statement, indicating