Question 1

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

The answer of A manufacturer wants to estimate the proportion...

Question 2

A newspaper wants to estimate the proportion of Americans who will vote for Candidate A. A random sample of 1000 voters is taken. Of the 1000 respondents, 526 say that they will vote for Candidate A. Which Excel function would be used to construct a confidence interval estimate?

Accepted Answer

NORM.S.INV is the Excel function used to construct a confidence interval estimate for the proportion of Americans who will vote for Candidate A.

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. If the sample mean is 9 hours, then the 95% confidence interval is approximately

Accepted Answer

The 95% confidence interval is calculated using the formula: sample mean ± (Z * (population standard deviation / √sample size)). With a Z value of 1.96 for 95% confidence, the interval is 9 ± (1.96 * (1.2 / √81)), which is approximately 8.74 to 9.26 hours.

Question 4

It is known that the population variance equals 484. With a 0.95 probability, the sample size that needs to be taken to estimate the population mean if the desired margin of error is 5 or less is

Accepted Answer

To find the sample size, use the formula for the margin of error in estimating a population mean: E = Z * (σ/√n), where E is the margin of error, Z is the Z-score for the desired confidence level (1.96 for 95%), σ is the population standard deviation (√484 = 22), and n is the sample size. Solving for n when E = 5 gives n ≈ 74.5, which rounds up to 75.

Question 5

To estimate a population mean, the sample size needed to provide a margin of error of 2 or less with a .95 probability when the population standard deviation equals 11 is

Accepted Answer

The answer of To estimate a population mean, the sample...

Question 6

The margin of error in an interval estimate of the population mean is a function of all of the following except

Accepted Answer

The sample mean is not a factor in determining the margin of error.

Question 7

For which of the following values of p is the value of p(1 - p) maximized?

Accepted Answer

The expression p(1 - p) is maximized when p = 0.5, as it forms a quadratic function that reaches its maximum at the vertex, which occurs at p = 0.5 for the standard form of a quadratic equation.

Question 8

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

The margin of error for a sample mean with known standard deviation is calculated using the formula: Margin of Error = Z * (σ/√n). For a 95% confidence level, Z is approximately 1.96. Given σ = 1 and n = 100, the margin of error is 1.96 * (1/√100) = 0.196.

Question 9

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

The formula for calculating the standard error of the mean is
standard error of the mean = population standard deviation / square root of sample size.
Substituting the values given, we get
standard error of the mean = 1.2 / square root of 81 = 0.133. Therefore, the best choice is D.

Question 10

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. The 95% confidence interval for the average checkout time of all customers is

Accepted Answer

We can use the formula for a confidence interval for a population mean with known standard deviation:
CI = x̄ ± z*(σ/√n)
where x̄ is the sample mean, σ is the population standard deviation, n is the sample size, and z is the critical value for the desired confidence level. With a 95% confidence level, z = 1.96.
Plugging in the given values, we get:
CI = 3.0 ± 1.96*(1/√100)
CI = 3.0 ± 0.196
CI = (2.804, 3.196)
Therefore, the 95% confidence interval for the average checkout time of all customers is (2.804, 3.196).

Question 11

Exhibit 8-3
A random sample of 81 automobiles traveling on a section of an interstate showed an average speed of 60 mph. The distribution of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph.
-Refer to Exhibit 8-3. The value to use for the standard error of the mean is

Accepted Answer

The standard error of the mean is calculated as the standard deviation divided by the square root of the sample size: 13.5 / √81 = 1.5.

Question 12

Using an $\alpha$ = 0.04, a confidence interval for a population proportion is determined to be 0.65 to 0.75. If the level of significance is decreased, the interval for the population proportion

Accepted Answer

Decreasing the level of significance (increasing the confidence level) results in a wider confidence interval, as it requires more certainty that the interval contains the true population proportion.

Question 13

We can use the normal distribution to make confidence interval estimates for the population proportion, p, when

Accepted Answer

Both conditions np ≥ 5 and n(1-p)≥ 5 should be met to use normal distribution for confidence interval estimates for population proportion, p.

Question 14

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. If the confidence coefficient is reduced to 0.80, the standard error of the mean

Accepted Answer

The standard error of the mean is calculated using the formula: standard deviation divided by the square root of the sample size. It is not affected by changes in the confidence coefficient.

Question 15

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

Accepted Answer

The degrees of freedom associated with a t distribution are a function of the sample size. As the sample size increases, the degrees of freedom increase, which means the t distribution becomes closer to the standard normal distribution. The area in the upper tail, sample standard deviation, and confidence coefficient do not directly affect the degrees of freedom.

Question 16

The general form of an interval estimate of a population mean or population proportion is the _____ plus and minus the _____.

Accepted Answer

The general form of an interval estimate of a population mean or population proportion is a point estimate plus and minus the margin of error. The other options do not represent the correct general form of an interval estimate.

Question 17

In determining the sample size necessary to estimate a population proportion, which of the following information is not needed?

Accepted Answer

The mean of the population is not necessary to determine the sample size for estimating a population proportion. The maximum margin of error, confidence level, and preliminary estimate of the true population proportion are all needed to calculate the sample size.

Question 18

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. The standard error of the mean equals

Accepted Answer

The standard error of the mean is calculated as the standard deviation divided by the square root of the sample size. Here, it is 1 minute divided by the square root of 100, which equals 0.100.

Question 19

Exhibit 8-3
A random sample of 81 automobiles traveling on a section of an interstate showed an average speed of 60 mph. The distribution of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph.
-Refer to Exhibit 8-3. If we are interested in determining an interval estimate for $\mu$ at 86.9% confidence, the z value to use is

Accepted Answer

For an 86.9% confidence interval, the z value corresponds to the middle 86.9% of the standard normal distribution, which is approximately 1.51.

Question 20

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

The margin of error is calculated as:Margin of error = z * (standard deviation / square root of sample size)where z is the z-score corresponding to the desired confidence level. For a 0.95 confidence level, z = 1.96.Plugging in the values, we get:Margin of error = 1.96 * (1.2 / square root of 81) = 0.26 hoursTherefore, the margin of error is approximately 0.26 hours.

Quiz 8: Interval Estimation

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?

A newspaper wants to estimate the proportion of Americans who will vote for Candidate A. A random sample of 1000 voters is taken. Of the 1000 respondents, 526 say that they will vote for Candidate A. Which Excel function would be used to construct a confidence interval estimate?

It is known that the population variance equals 484. With a 0.95 probability, the sample size that needs to be taken to estimate the population mean if the desired margin of error is 5 or less is

To estimate a population mean, the sample size needed to provide a margin of error of 2 or less with a .95 probability when the population standard deviation equals 11 is

The margin of error in an interval estimate of the population mean is a function of all of the following except

For which of the following values of p is the value of p(1 - p) maximized?

Using an $\alpha$ = 0.04, a confidence interval for a population proportion is determined to be 0.65 to 0.75. If the level of significance is decreased, the interval for the population proportion

We can use the normal distribution to make confidence interval estimates for the population proportion, p, when

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

The general form of an interval estimate of a population mean or population proportion is the _ plus and minus the _.

In determining the sample size necessary to estimate a population proportion, which of the following information is not needed?

Quiz 8: Interval Estimation

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?

A newspaper wants to estimate the proportion of Americans who will vote for Candidate A. A random sample of 1000 voters is taken. Of the 1000 respondents, 526 say that they will vote for Candidate A. Which Excel function would be used to construct a confidence interval estimate?

It is known that the population variance equals 484. With a 0.95 probability, the sample size that needs to be taken to estimate the population mean if the desired margin of error is 5 or less is

To estimate a population mean, the sample size needed to provide a margin of error of 2 or less with a .95 probability when the population standard deviation equals 11 is

The margin of error in an interval estimate of the population mean is a function of all of the following except

For which of the following values of p is the value of p(1 - p) maximized?

Using an α\alphaα = 0.04, a confidence interval for a population proportion is determined to be 0.65 to 0.75. If the level of significance is decreased, the interval for the population proportion

We can use the normal distribution to make confidence interval estimates for the population proportion, p, when

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

The general form of an interval estimate of a population mean or population proportion is the _____ plus and minus the _____.

In determining the sample size necessary to estimate a population proportion, which of the following information is not needed?

Using an $\alpha$ = 0.04, a confidence interval for a population proportion is determined to be 0.65 to 0.75. If the level of significance is decreased, the interval for the population proportion

The general form of an interval estimate of a population mean or population proportion is the _ plus and minus the _.