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
The personnel director of a large corporation wishes to study absenteeism among clerical workers at the central office during the year. A random sample of 25 clerical workers revealed the following: _ Absenteeism: x = 9.7 days and S = 4.0 days 12 clerical workers were absent more than 10 days What
A statistician wishes to estimate the average total compensation of CEOs in the service industry. Data were randomly collected from 18 CEOs and the 97% confidence interval was calculated to be ($2,181,260, $5,836,180). Which of the following interpretations is correct? A. 97% of the sampled total compensation values fell bet
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
A confidence interval was used to estimate the proportion of statistics students that are female. A random sample of 72 statistics students generated the following 90% confidence level ( 0.438, 0.642). Using this information what size sample would be necessary if we wanted to estimate the true proportion to within plus/minus 0.0
The width of a confidence interval estimate for a proportion will be: A. narrower for 99% confidence than for 95% confidence B. wider for a sample size of 100 than for a sample size of 50 C. narrower for 90% confidence than for 95% confidence D. narrower when the sample proportion is 0.50 than when the sample proportion is
If you were constructing a 99% confidence interval of the population mean based on a sample of n = 25 where the standard deviation of the sample s=0.05, the critical value of t will be: A. 2.7969 B. 2.7874 C. 2.4922 D. 2.4851.
What do we mean by confidence intervals? What do the 'tails' of a distribution signify? Provide an example of a one tailed problem.
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.
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.
Provide specific examples for how to establish confidence intervals when making business decisions.
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
(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
We use testing of hypothesis - Z-test to test significant difference between means and proportions. See attached file for full problem description.
A researcher wants to estimate the difference in the means of two populations. A random sample of 36 items from the first population results in a sample mean of 430 with a sample standard deviation of 120. A random sample of 49 items from the second population results in a sample mean of 460 with a sample standard deviation of 1
A researcher desires to estimate the difference in means of two populations. To accomplish this, she takes a random sample of 81 items from the first population. The sample yields a mean of 168 with a variance of 324. A random sample of 64 items is taken from the second population yielding a mean of 161 with a variance of 625. C
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
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)
(1) For a t distribution with 12 degrees of freedom, find the area, or probability, that is in each region: (A)To the left of 1.782 (B)To the right of -1.356 (C)To the right of 2.681 (D)To the left of -1.782 (E)Between -2.179 and +2.179 (F)Between -1.356 and +1.782 (2) Due to constituents' complaints to their representa
A toy manufacturer wants to see how long, on average, a new toy captures children's attention. He tests 13 children selected at random and finds that their mean attention span is 35 minutes with a standard deviation of 6 minutes. If we assume that attention spans are normally distributed, find a 90 % confidence interval for t
The union for a particular industry has determined that the standard deviation of the daily wages of its workers is $20. A random sample of 100 workers in this industry has a mean daily wage of $116. Find a 95% confidence interval for the true mean daily wage of all union workers in the industry. Then complete the table below.
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
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
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
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.
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?
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?
Construct a graph determining the probability for the following problems. The sample mean and sample standard deviation are present. Construct a 90% confidence interval using the population mean and sample size.
(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
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