Explore BrainMass

Confidence Interval

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

Determining whether it is sample 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

Confidence Intervals

A. Test is the difference in lifetime of vehicles exist between the two manufacturers at a=0.01. Please see attached.

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

Statistics: Margin of Error, Sample Sizes and Confidence Intervals

Question: Give an estimate of the sample size needed to obtain the specified margin of error for a 95% confidence interval. Margin of error = 0.01, standard deviation = 0.25 Scenario: Researchers want to determine the mean number of hours students spend watching TV. A margin of error of 0.25 hour is desired. Past studies

Normal Distribution, Sampling distribution, Confidence interval

1) The distribution of sample mean for samples of 500 homes is normal with a mean of 2.64 and a standard deviation of 0.06. Suppose you select a random sample of n=500 homes and determine that the mean number of people per home for this sample id 2.55. How many standard deviations is the sample mean of the sampling distribution?

Basic Business Statistics: 17 Multiple choice questions on Sampling distribution, Normal Distribution, t-distribution, confidence interval estimate, standard error of the mean, finite population correction factor, sample size, degrees of freedom, one-sided confidence interval estimate

Please see attached. 1. For air travelers, one of the biggest complaints is of the waiting time between when the airplane taxis away from the terminal until the flight takes off. This waiting time is known to have a skewed-right distribution with a mean of 10 minutes and a standard deviation of 8 minutes. Suppose 100 flights ha

Statistics : Confidence Interval and Z-Statistic

In the spring of 2002, residents of the United States were quite worried about the possibility of further terrorists attacks. To gauge the public's sentiment on this topic, the Gallup Poll asked 1002 U.S. adults the following question during May 20-22, 2002. How likely is it that there will be further acts of terrorism in the

Proportions and Confidence Interval

1) Does the M&M/Mars Corporation use the same proportion of red candies in its plain and peanut varieties? A random sample of 56 plains M&Ms contained 12 red candies, and another random sample of 32 peanut M&Ms contained 8 red candies. a) Construct a 95% confidence interval for the difference in the proportions of red candies f

Point Estimate, Margin of Error and Confidence Interval

1) In an attempt to compare the starting salaries of college graduates majoring in education and social sciences, random samples of 50 recent college graduates in each major were selected and the attached information was obtained. (see attachment for data table) a) Find a point estimate for the difference in the average sta

Margin of error and statistical testing

Question: Do you have university education? Yes=45% (n=450) No=60% (n=800) To find out whether 45% is significantly different from 60%, I use this: =SQRT (45*(100-45)*1.96*1.96/450) answer=4.59 Then I use =SQRT(+60*(100-60)*1.96*1.96/800) answer=3.40 Then I calculate the total margin of error

Confidence Interval; Sampling Distribution; Mean and Standard Deviation

1. A parcel service randomly selected 48 packages it received. The sample has a mean weight of 18.6 pounds. Assume that σ = 3.4 pounds. Construct a 90% confidence interval for the true mean weight, μ, of all packages received by the parcel service. 2. A phone company wants to estimate the mean duration of local

P-Values, Null Hypotheses and Confidence Intervals

I have some trouble understanding the concept first and it will be really helpful if I can see the problem worked out. Here is example question from the textbook. Please help me. The data studies the effect of dietary calcium on blood pressure. In the experiment, one group of black male adults received calcium supplements f