What can you do to decrease the margin of error?

Check all the answers that apply.

a

Decrease the sample size

b

Increase the confidence level

c

Increase the sample size

d

Nothing you do can decrease the margin of error

e

Decrease the confidence level

Question 7(1 point)

Increasing the margin of error would result in a confidence interval that is _______ .

narrower

wider

Question 8(1 point)

A political poll was conducted by calling land-line telephones. The researchers conducting the poll are concerned about the possibility of undercoverage because some people do not own a phone or own only a cell phone. Which of the following is the best way for them to correct for this source of bias?

a

Throw this sample out and start over again with a better sampling method.

b

Use a higher confidence level, such as 99%.

c

Use a lower confidence level, such as 90%.

d

Select a larger sample.

Find the following critical values:

Column A1.

Find Z* for a C-Level of 95% and n = 25:

Find Z* for a C-Level of 95% and n = 25

2.

Find Z* for a C-Level of 99% and n = 20:

Find Z* for a C-Level of 99% and n = 20

3.

Find t* for a C-Level of 90% and n = 28:

Find t* for a C-Level of 90% and n = 28

4.

Find t* for a C-Level of 95% and n = 63:

Find t* for a C-Level of 95% and n = 63

Column Ba.

1.703

b.

2.576

c.

3.291

d.

1.960

e.

1.990

f.

2.000

g.

1.701

Question 10(1 point)

A political pollster wants to know what proportion of voters are planning to vote for the incumbent candidate in an upcoming election. A poll of 150 randomly selected voters is taken from the more than 2,000 voters in the population, and 78 of those selected plan to vote for the incumbent candidate.

Based on this sample, which of the following is a 90% confidence interval for the proportion of all voters who plan to vote for the incumbent candidate?

Question 11(1 point)

A safety specialist was concerned about cars' speeds on a certain busy stretch of road. They randomly selected 21 cars and measured their speeds at the same point on the road. Each car was from a different time period and day, so the specialist is willing to consider the sample as representative. The speeds in the sample were strongly skewed to the left with a sample mean of 96.5 km/hr and a standard deviation of 4.3 km/hr.

Based on this sample, which of the following is a 95% confidence interval for the mean speed.

Question 12(1 point)

A nutritionist wants to estimate the average caloric content of the burritos at a popular restaurant. They obtain a random sample of 14 burritos and measure their caloric content. Their sample data are roughly symmetric with a mean of 700 calories and a standard deviation of 50 calories.

Based on this sample, which of the following is a 95% confidence interval for the mean caloric content of these burritos?