Explore BrainMass

Confidence Interval

Calculate a 99 percent confidence interval for μ

The weight of a product is measured in pounds. A sample of 50 units is taken from a batch. The sample yielded the following results: = 75 lbs., and s = 10 lbs. Calculate a 99 percent confidence interval for μ.

Solutions to Various Statistics Problems

1. Each day of the year a large sample of cellular phone calls is selected and a 95% confidence interval is calculated for the mean length of all cellular phone calls on that day. Of these 365 confidence intervals, one for each day of the year, approximately how many will cover their respective population means? Explain your rea

Upper Bounds, One Sided Confidence Interval: Online Fashion Store

An internal control policy for an online fashion accessories store requires a quality assurance check before a shipment is made. The tolerable exception rate for this internal control is 0.05. During an audit, 500 shipping records were sampled from a population of 5,000 shipping records and 12 were found that violated the cont

The strength is a function of heating time

Please provide insight An experiment was performed on a certain metal to determine if the strength is a function of heating time. 95% confidence interval for the average strength of a metal sheet when the average heating time is 4 minutes is from 4.325 to 5.675. Provide a managerial interpretation of this interval.

Confidence Intervals & Tails

What do we mean by confidence intervals? What do the 'tails' of a distribution signify? Provide an example of a one tailed problem.

Confidence Interval & Probable Value

Confidence intervals are frequently used to assess a population and determine the probable value for a population parameter. I need an application or example pertaining to Customs & immigration and the farming business. Please describe your examples.

Probability in Business Decision Making

1. What is the role of probability concepts in business decision making? 2. Define probability concepts. 3. Give two examples that are related to the farming Industry or any other Industry or professional environment. THANK YOU, your help is greatly appreciated.

Comparing population means

Comparing Two Population Means Instructor Reputation and Teacher Ratings (revisited) How powerful are rumors? Frequently, students ask friends and/or look at instructor evaluations to decide if a class is worth taking. Kelley (1950) found that instructor reputation has a profound impact on actual teaching ratings. Towler a

Notes on Scattergrams, hypothesis, confidence interval

(See attached file for full problem description) --- 1.7 Based on the data for the years 1962 to 1977 for the United States, Dale Bails and Larry Peppers17 obtained the following demand function for automobiles: Yt = 5807 + 3.24Xt r2 = 0.22 Se = (1.634) Where Y = retail sales of passenger cars (thou

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

A biologist with the Department of Agriculture is studying the growth of artichokes. She knows that the number of artichokes produced by each plant follows a distribution which is approximately normal. She collects a sample of six plants and counts the number of artichokes produced by each plant. Here are her results: 32 17

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

Probability and Statistics - Confidence Interval

The 2 problems attached are problems from the topic Confidence Intervals for the Variance and Standard Deviation of a Normal Proportion. Please provide a very detailed solution to the problems.

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?

Another Confidence Interval Proof

(See attached file for full problem description) --- For large sample sizes, n, the sampling distribution of the sample standard deviation S is sometimes approximated with a Normal distribution having mean and variance. Prove that this approximation leads to the following large-sample confidence interval for the population

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

Point Estimation and Confindence Intervals of Quartiles

The following data are the lifetimes (in hours) of 20 certain electrical components: 6278 3113 9350 5236 11584 12628 7725 8604 14266 6215 3212 9003 3523 12888 9460 13431 17809 2812 11825 2398 Find a point estimate and 90% confidence interval for the population lower quartile. Can you explain how and why we do the foll

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