Exam 8: Confidence Interval Estimation

Instruction 8-14 A sales and marketing management magazine conducted a survey on salespeople cheating on their expense reports and other unethical conduct.In the survey on 200 managers,58% of the managers have caught salespeople cheating on an expense report,50% have caught salespeople working a second job on company time,22% have caught salespeople listing a "strip bar" as a restaurant on an expense report,and 19% have caught salespeople giving a kickback to a customer. -Referring to Instruction 8-14,we are 95% confident that the population mean number of managers who have caught salespeople cheating on an expense report is between 0.5116 to 0.6484.

Instruction 8-7 After an extensive advertising campaign,the manager of a company wants to estimate the proportion of potential customers that recognise a new product.She samples 120 potential consumers and finds that 54 recognise this product.She uses this sample information to obtain a 95% confidence interval that goes from 0.36 to 0.54. -Referring to Instruction 8-7,95% of the time,the sample proportion of people that recognise the product will fall between 0.36 and 0.54.

The head librarian at the National Library of Australia has asked her assistant for an interval estimate of the mean number of books checked out each day.The assistant provides the following interval estimate: from 740 to 920 books per day.If the head librarian knows that the population standard deviation is 150 books checked out per day,approximately how large a sample did her assistant use to determine the interval estimate?

Which of the following is NOT true about the Student's t distribution?

The difference between the sample size and the population size is called the sampling error.

Instruction 8-14 A sales and marketing management magazine conducted a survey on salespeople cheating on their expense reports and other unethical conduct.In the survey on 200 managers,58% of the managers have caught salespeople cheating on an expense report,50% have caught salespeople working a second job on company time,22% have caught salespeople listing a "strip bar" as a restaurant on an expense report,and 19% have caught salespeople giving a kickback to a customer. -Referring to Instruction 8-14,construct a 95% confidence interval estimate of the population proportion of managers who have caught salespeople giving a kickback to a customer.

Instruction 8-10 The Registrar of a university would like to estimate the proportion of the student population who owns a personal computer.In a sample of 500 students,417 own a personal computer. -Referring to Instruction 8-10,a 99% confidence interval for the proportion of student population who own a personal computer is from ________ to ________.

Instruction 8-13 A university wanted to find out the percentage of students who felt comfortable reporting cheating by their fellow students.A surveyed of 2,800 students was conducted and the students were asked if they felt comfortable reporting cheating by their fellow students.The results were 1,344 answered "YES" and 1,456 answered "NO". -Referring to Instruction 8-13,a 90% confidence interval calculated from the same data would be narrower than a 99% confidence interval.

Instruction 8-7 After an extensive advertising campaign,the manager of a company wants to estimate the proportion of potential customers that recognise a new product.She samples 120 potential consumers and finds that 54 recognise this product.She uses this sample information to obtain a 95% confidence interval that goes from 0.36 to 0.54. -Referring to Instruction 8-7,this interval requires the use of the t distribution to obtain the confidence coefficient.

Instruction 8-11 The principal of a high school of a small suburb wants to make sure that no more than 5% of the students skip more than 10 days of school in a year.A random sample of 145 students from a population of 800 showed that 12 students skipped more than 10 days of school last year. -Referring to Instruction 8-11,the principle can conclude with 95% level of confidence that no more than 5% of the students in the high school skipped more than 10 days of school last year.

Instruction 8-13 A university wanted to find out the percentage of students who felt comfortable reporting cheating by their fellow students.A surveyed of 2,800 students was conducted and the students were asked if they felt comfortable reporting cheating by their fellow students.The results were 1,344 answered "YES" and 1,456 answered "NO". -Referring to Instruction 8-13,a 99% confidence interval will contain 99% of the student population who feel comfortable reporting cheating by their fellow students.

Instruction 8-8 A hotel chain wants to estimate the average number of rooms rented daily in each month.The population of rooms rented daily is assumed to be normally distributed for each month with a standard deviation of 24 rooms. -Referring to Instruction 8-8,during February,a sample of 25 days has a sample mean of 37 rooms.Use this information to calculate a 92% confidence interval for the population mean.

Instruction 8-7 After an extensive advertising campaign,the manager of a company wants to estimate the proportion of potential customers that recognise a new product.She samples 120 potential consumers and finds that 54 recognise this product.She uses this sample information to obtain a 95% confidence interval that goes from 0.36 to 0.54. -Referring to Instruction 8-7,it is possible that the true proportion of people that recognise the product is not between 0.36 and 0.54.

Instruction 8-5 The actual voltages of power packs labelled as 12 volts are as follows: 11.77,11.90,11.64,11.84,12.13,11.99,and 11.77. -Referring to Instruction 8-5,the critical value for a 99% confidence interval for this sample is ________.

The confidence interval estimate of the population proportion is constructed around the sample proportion.

Suppose a 95% confidence interval for μ turns out to be (1,000,2,100).What type of reasoning would you make when defining what "95% confident" means about the population?

Instruction 8-14 A sales and marketing management magazine conducted a survey on salespeople cheating on their expense reports and other unethical conduct.In the survey on 200 managers,58% of the managers have caught salespeople cheating on an expense report,50% have caught salespeople working a second job on company time,22% have caught salespeople listing a "strip bar" as a restaurant on an expense report,and 19% have caught salespeople giving a kickback to a customer. -Referring to Instruction 8-14,determine the sample size needed to estimate the proportion of managers who have caught salespeople working a second job on company time to within ±0.02 with 95% confidence.

Instruction 8-14 A sales and marketing management magazine conducted a survey on salespeople cheating on their expense reports and other unethical conduct.In the survey on 200 managers,58% of the managers have caught salespeople cheating on an expense report,50% have caught salespeople working a second job on company time,22% have caught salespeople listing a "strip bar" as a restaurant on an expense report,and 19% have caught salespeople giving a kickback to a customer. -Referring to Instruction 8-14,construct a 95% confidence interval estimate of the population proportion of managers who have caught salespeople working a second job on company time.

Instruction 8-7 After an extensive advertising campaign,the manager of a company wants to estimate the proportion of potential customers that recognise a new product.She samples 120 potential consumers and finds that 54 recognise this product.She uses this sample information to obtain a 95% confidence interval that goes from 0.36 to 0.54. -Referring to Instruction 8-7,it is possible that the true proportion of people that recognise the product is between 0.36 and 0.54.

Instruction 8-2 The managers of a company are worried about the morale of their employees.In order to determine if a problem in this area exists,they decide to evaluate the attitudes of their employees with a standardised test.They select the Fortunato test of job satisfaction,which has a known standard deviation of 24 points. -Referring to Instruction 8-2,due to financial limitations,the managers decide to take a sample of 45 employees.This yields a mean score of 88.0 points.A 90% confidence interval would go from ________ to ________.