Question 1

The degrees of freedom associated with a t distribution are a function of the

Accepted Answer

A)  area in the upper tail 
B) sample standard deviation 
C)  confidence coefficient 
D)  sample size 
A)  area in the upper tail 
B) sample standard deviation 
C)  confidence coefficient 
D)  sample size

Question 2

Exhibit 8-1
In order to estimate the average time spent on the computer terminals per student at a local university, data were collected from a sample of 81 business students over a one-week period. Assume the population standard deviation is 1.2 hours.
-Refer to Exhibit 8-1. With a 0.95 probability, the margin of error is approximately

Accepted Answer

A) 0.26 
B) 1.96 
C) 0.21 
D) 1.64 
A) 0.26 
B) 1.96 
C) 0.21 
D) 1.64

Question 3

Exhibit 8-1
In order to estimate the average time spent on the computer terminals per student at a local university, data were collected from a sample of 81 business students over a one-week period. Assume the population standard deviation is 1.2 hours.
-Refer to Exhibit 8-1. The standard error of the mean is

Accepted Answer

A) 7.5 
B) 0.014 
C) 0.160 
D) 0.133 
A) 7.5 
B) 0.014 
C) 0.160 
D) 0.133

Question 4

The Highway Safety Department wants to study the driving habits of individuals. A sample of 41 cars traveling on the highway revealed an average speed of 60 miles per hour and a standard deviation of 7 miles per hour. The population of car speeds is approximately normally distributed. Determine a 90% confidence interval estimate for the speed of all cars.

Accepted Answer

The answer of The Highway Safety Department wants to study...

Question 5

From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for $\mu$. Which of the following statements is true?

Accepted Answer

A) The standard normal distribution can be used. 
B) The t distribution with 50 degrees of freedom must be used. 
C) The t distribution with 49 degrees of freedom must be used. 
D) The sample size must be increased in order to develop an interval estimate. 
A) The standard normal distribution can be used. 
B) The t distribution with 50 degrees of freedom must be used. 
C) The t distribution with 49 degrees of freedom must be used. 
D) The sample size must be increased in order to develop an interval estimate.

Question 6

If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be

Accepted Answer

A) 0.1 
B) 0.95 
C) 0.9 
D) 0.05 
A) 0.1 
B) 0.95 
C) 0.9 
D) 0.05

Question 7

A random sample of 36 students at a community college showed an average age of 25 years. Assume the ages of all students at the college are normally distributed with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all students at this college is

Accepted Answer

A) 24.301 to 25.699 
B) 24.385 to 25.615 
C) 23.200 to 26.800 
D) 23.236 to 26.764 
A) 24.301 to 25.699 
B) 24.385 to 25.615 
C) 23.200 to 26.800 
D) 23.236 to 26.764

Question 8

The z value for a 97.8% confidence interval estimation is

Accepted Answer

A) 2.02 
B) 1.96 
C) 2.00 
D) 2.29 
A) 2.02 
B) 1.96 
C) 2.00 
D) 2.29

Question 9

A random sample of 100 credit sales in a department store showed an average sale of $120.00. From past data, it is known that the standard deviation of the population is $40.00.
a.Determine the standard error of the mean.
b.With a 0.95 probability, determine the margin of error.
c.What is the 95% confidence interval of the population mean?

Accepted Answer

a.4.00
b.7

Question 10

A random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population mean is

Accepted Answer

A) 15.2 to 24.8 
B) 19.2 to 20.8 
C) 19.216 to 20.784 
D) 21.2 to 22.8 
A) 15.2 to 24.8 
B) 19.2 to 20.8 
C) 19.216 to 20.784 
D) 21.2 to 22.8

Question 11

A random sample of 81 students at a local university showed that they work an average of 100 hours per month. The population standard deviation is known to be 27 hours. Compute a 95% confidence interval for the mean hours per month all students at the university work.

Accepted Answer

The answer of A random sample of 81 students at...

Question 12

A simple random sample of 25 items from a normally distributed population resulted in a sample mean of 28 and a standard deviation of 7.5. Construct a 95% confidence interval for the population mean.

Accepted Answer

The answer of A simple random sample of 25 items...

Question 13

The makers of a soft drink want to identify the average age of its consumers. A sample of 16 consumers is taken. The average age in the sample was 22.5 years with a standard deviation of 5 years. Assume the population of consumer ages is normally distributed.
a.Construct a 95% confidence interval for the average age of all the consumers.
b.Construct an 80% confidence interval for the average age of all the consumers.
c.Discuss why the 95% and 80% confidence intervals are different.

Accepted Answer

a.19.836 to 25.164
b.20.824 to

Question 14

A marketing firm is developing a new television advertisement for a large discount retail chain. A sample of 30 people is shown two potential ads and asked their preference. The results for ad #1 follow. Use Excel to develop a 95% confidence interval estimate of the proportion of people in the population who will prefer ad #1.

Accepted Answer

The answer of A marketing firm is developing a new...

Question 15

A manufacturer wants to estimate the proportion of defective items that are produced by a certain machine. A random sample of 50 items is taken. Which Excel function would not be appropriate to construct a confidence interval estimate?

Accepted Answer

A) NORM.S.INV 
B) COUNTIF 
C) STDEV 
D) All are appropriate. 
A) NORM.S.INV 
B) COUNTIF 
C) STDEV 
D) All are appropriate.

Question 16

A local hotel wants to estimate the proportion of its guests that are from out-of-state. Preliminary estimates are that 45% of the hotel guests are from out-of-state. How large a sample should be taken to estimate the proportion of out-of-state guests with a margin of error no larger than 5% and with a 95% level of confidence?

Accepted Answer

The answer of A local hotel wants to estimate the...

Question 17

Exhibit 8-2
The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customers to check out was 3.0 minutes. It is known that the standard deviation of the checkout time is one minute.
-Refer to Exhibit 8-2. With a .95 probability, the sample mean will provide a margin of error of

Accepted Answer

A) 0.95 
B) 0.10 
C) .196 
D) 1.96 
A) 0.95 
B) 0.10 
C) .196 
D) 1.96

Question 18

A coal company wants to determine a 95% confidence interval estimate for the average daily tonnage of coal that they mine. Assuming that the company reports that the standard deviation of daily output is 200 tons, how many days should they sample so that the margin of error will be 39.2 tons or less?

Accepted Answer

The answer of A coal company wants to determine a...

The degrees of freedom associated with a t distribution are a function of the

From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for $\mu$ . Which of the following statements is true?

If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be

A random sample of 36 students at a community college showed an average age of 25 years. Assume the ages of all students at the college are normally distributed with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all students at this college is

The z value for a 97.8% confidence interval estimation is

A random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population mean is

A random sample of 81 students at a local university showed that they work an average of 100 hours per month. The population standard deviation is known to be 27 hours. Compute a 95% confidence interval for the mean hours per month all students at the university work.

A simple random sample of 25 items from a normally distributed population resulted in a sample mean of 28 and a standard deviation of 7.5. Construct a 95% confidence interval for the population mean.

A manufacturer wants to estimate the proportion of defective items that are produced by a certain machine. A random sample of 50 items is taken. Which Excel function would not be appropriate to construct a confidence interval estimate?

Data and Statistics

Descriptive Statistics: Tabular and Graphical Displays

Descriptive Statistics: Numerical Measures

Introduction to Probability

Discrete Probability Distributions

Continuous Probability Distributions

Sampling and Sampling Distributions

Hypothesis Tests

Inference About Means and Proportions With Two Populations

Inferences About Population Variances

Tests of Goodness of Fit, Independence and Multiple Proportions

Experimental Design and Analysis of Variance

Simple Linear Regression

Multiple Regression

Regression Analysis: Model Building

Time Series Analysis and Forecasting

Nonparametric Methods

Statistical Methods for Quality Control

Decision Analysis

Sample Survey

Filters

Exam 8: Interval Estimation

The degrees of freedom associated with a t distribution are a function of the

From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for μ\muμ . Which of the following statements is true?

If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be

A random sample of 36 students at a community college showed an average age of 25 years. Assume the ages of all students at the college are normally distributed with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all students at this college is

The z value for a 97.8% confidence interval estimation is

A random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population mean is

A random sample of 81 students at a local university showed that they work an average of 100 hours per month. The population standard deviation is known to be 27 hours. Compute a 95% confidence interval for the mean hours per month all students at the university work.

A simple random sample of 25 items from a normally distributed population resulted in a sample mean of 28 and a standard deviation of 7.5. Construct a 95% confidence interval for the population mean.

A manufacturer wants to estimate the proportion of defective items that are produced by a certain machine. A random sample of 50 items is taken. Which Excel function would not be appropriate to construct a confidence interval estimate?

Data and Statistics

Descriptive Statistics: Tabular and Graphical Displays

Descriptive Statistics: Numerical Measures

Introduction to Probability

Discrete Probability Distributions

Continuous Probability Distributions

Sampling and Sampling Distributions

Hypothesis Tests

Inference About Means and Proportions With Two Populations

Inferences About Population Variances

Tests of Goodness of Fit, Independence and Multiple Proportions

Experimental Design and Analysis of Variance

Simple Linear Regression

Multiple Regression

Regression Analysis: Model Building

Time Series Analysis and Forecasting

Nonparametric Methods

Statistical Methods for Quality Control

Decision Analysis

Sample Survey

Filters

From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for $\mu$ . Which of the following statements is true?