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Confidence Interval

Standard Error, Confidence Interval and Hypothesis Testing

I need some help with these hypothesis testing and standard error questions: 1. The mean of a normal probability distribution is 60; the standard deviation is 5. (a) About what percent of the observations lie between 55 and 65? (b) About what percent of the observations lie between 50 and 70? (c) About what percent of the

Difference Between Two Population Means

An experiment to compare the tension bond strength of polymer latex modified mortar (Portland cement mortar to which polymer latex emulsions have been added during mixing) to that of unmodified mortar resulted in x-bar = 18.12 kgf/cm^2 for the modified mortar (m = 40) and y-bar = 16.87 kgf/cm^2 for the unmodified mortar (n = 32)

Confidence interval

The Bureau of Labor Statistics (BLS) uses 90% confidence in presenting unemployment results from the monthly Current Population Survey (CPS). The Jan. 2000 survey interviewed 133,357 members of the civialian labor force. Of these, 6264 were unemployed. The CPS is not a simple random sample, but for the purposes of this exercise

Develop a 99 percent confidence interval for the population mean. Construct a 95 percent confidence interval for the mean number of misspelled words in the population of student essays. Construct the 99 percent confidence interval for the population proportion. The estimate is to be within $100. How many families should be interviewed?

7. Bob Nale is the owner of Nale's Texaco GasTown. Bob would like to estimate the mean number of gallons of gasoline sold to his customers. From his records, he selects a random sample of 60 sales and finds the mean number of gallons sold is 8.60 and the standard deviation is 2.30 gallons. a. What is the point estimate of the

Confidence interval

The average number of textbooks received per year by 100 college professors at GCU is 30 with a standard deviation of 3. What is the 99% confidence interval of the true mean?

Confidence interval

A random sample of 16 women in a beginning aerobics class had a mean weight of 142 pounds and a standard deviation of 12 pounds. What is the 95% confidence interval of the mean weight of all women in the aerobics class?

Confidence Intervals, Proportions, Mean, Standard Deviation

1. Three hundred of 450 drivers surveyed indicated that they would consider bying retread tires. Find a 95% confidence interval for the true proportion of all who might buy retread tires. 2. Insurance industry analysts report that the average amount of life insurance in effect in Virginia is $92,500 with a sample standard de

What is the 95% confidence interval estimate of u?

1) Suppose that 64 smokers were sampled. Assume the sample mean and the sample standard deviation remained the same ($20 and $5, respectively). a. What is the 95% confidence interval estimate of u? b. A research a firm a conducted a survey to det

Sample Size in Validity Studies

I am struggling with this portion of my assignment, please provide guidance. Using the attached article, provide an overview of the contents and apply the concepts to the Job Satisfaction survey. It is important to cover the concept of the techniques used to estimate sample size. See attachments.

The real estate data is now in an excel spreadsheet

UPDATE - Part B is the most important - if you are only able to help with that part, please do so. Refer to the Real Estate data, which reports information on homes sold in Denver, Colorado,last year. a. Let selling price be the dependent variable and size of the home the independent variable. Determine the regression e

Means and Confidence Levels

Dr. Walker is an industrial psychologist. She is currently studying stress among executives of Internet companies. She has developed a questionnaire that she believes measures stress. A score above 80 indicates stress at a dangerous level. A random sample of 15 executives revealed the following stress level scores. 94 78

Mean, variance, confidence interval

1. Compute the mean and variance of the following discrete probability distribution. x P(x ) 0 .20 1 .40 2 .30 3 .10 2. In a binomial situation n = 4 and π = .25. Determine the probabilities of the followi

Confidence Interval Estimation, Mean and Standard Deviation

Confidence Interval Estimation 1. Compute a 95% confidence interval for the population mean, based on the sample 1, 2, 3, 4, 5, 6, and 30. Change the number from 30 to 10 and recalculate the confidence interval. Using the results, describe the effect of an outlier or extreme value on the confidence interval. 7.285714 mean 1

Normal Distribution: proportion, probability, confidence interval, sample size,

1. Suppose that the mean income of all Mudville residents is $40,000 with a standard deviation of $6,000. Answer the following questions in terms of these data. a. What proportion of all possible samples of 36 Mudville residents would have a mean income of $38,000 or more? b. What is the probability of selecting a rando

Confidence Interval

Calculate a 95% confidence interval of the average number of Orlando Dining magazines sold over the last year. The average number sold per month is 11,500 and the standard deviation is 575.

Confidence interval and test of hypothesis

Please help with the following problems. The manager of a local bank wants to estimate the average amount held in checking accounts by the customers. A random sample of 30 customers is selected, and the results indicate a sample average of $4,750 and a sample standard deviation of $1,200. a) Set a 95% confidence interval

Confidence intervals

The inspection division of the Measures Department in a public service is interested in estimating the actual amount of soft drink that is placed in 2 -liter bottles at the local bottling plant of a large nationally known soft-drink company. The bottling plant has informed the inspection division that the standard deviation for

Normal Distribution: 68-95-99.7 Rule, Confidence Interval

1. The Environmental Protection Agency (EPA) fuel economy estimates for automobiles tested recently predicted a mean of 24.8 mpg with a standard deviation of 6.2 mpg for highway driving. Assume that the data is normally distributed. Using the 68-95-99.7 Rule, Determine: a. Within what interval you would expect the middle

Statistics: Standard Error and Sampling Size

Mr. James McWhinney, president of Daniel-James Financial Services, believes there is a relationship between the number of client contacts and the dollar amount of sales. To document this assertion, Mr. McWhinney gathered the following sample information. The X column indicates the number of client contacts last month, and the Y

Confidence Interval and Sampling Error

ComputerWare asked 500 of its iMac purchasers what computer they owned or had owned. There were 83 new computer owners, 60 who had owned a Windows-based computer, and 357 who had owned a Macintosh. The proportion of first-time computer owners was 83/500 = 0.167. So, 0.167 is an estimate of the proportion of new computer owners.


Need help with chapter review questions attached.

Statistics - data

Case study problem attached. --- The following are the number of chips per bag for the 42 bags of Chips Ahoy! analyzed. 1200 1219 1103 1213 1258 1325 1295 1247 1098 1185 1087 1377 1363 1121 1279 1269 1199 1244 1294 1356 1137 1545 1135 1143 1215 1402 1419 1166 1132 1514 1270 1345 1214 1154 1307 1293 1546 1228 1239 14

Confidence Interval Applications

Pulse rate is an important measure of the fitness of a person's cardiovascular system. The mean pulse rate for all U.S. adult males is approximately 72 heart beats per minute. A random sample of 21 U.S. male adults who jog at least 15 miles per week had a mean pulse rate of 52.6 beats per minute and a standard deviation of 3.22

What value would you expect to find for the standard deviation of the sample mean? Determine the minimum number of subjects to be polled for a survey with a margin of error of six percentage points and a confidence level of 95%. How many of the 200 confidence interval estimate should you expect to actually contain the population mean M? What is the standard deviation of this distribution?

16) If the random variable z is the standard normal distribution, then z(0.2324) = 23) Determine the minimum number of subjects to be polled for a survey with a margin of error of six percentage points and a confidence level of 95% a.253 b.267 c.278 d.306 e.none of these 32)

Statistic Confidence Level: Prediction interval in kilowatt hours

See attached file. a. Determine the .95 confidence interval, in thousands of kilowatt-hours, for the mean of all six-room homes. b. Determine the .95 prediction interval, in thousands of kilowatt-hours, for a particular six-room home. Number of Kilowatt-Hours Number of Kilowatt-Hours Rooms (thousands) Rooms (thous

Statistical Problems - Mean, Confidence Interval, Testing

1. The owner of Britten's Egg Farm wants to estimate the mean number of eggs laid per chicken. A sample of 20 chickens shows they laid an average of 20 eggs per month with a standard deviation of 2 eggs per month. a. What is the value of the population mean? What is the best estimate of this value? b. Explain why we need to