Confidence Interval Margin of Error

A survey was conducted where 150 high school students were asked the average amount of time they spent doing household chores in one week. The data collected resulted in a mean time of 180.5 minutes with a standard deviation of 5.5 minutes. Which of these represents a 95% confidence interval for the mean weekly hours spent doing household chores of all high school students?

• [171.5, 189.5]

• [175, 186]

• [178.3, 182.8]

• [179.6, 181.4]

Complete the following statement about the change in size. If your sample has a larger standard deviation, the ME will . . . .

• increase

• decrease

• stay the same

An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.

Find the Margin of Error to two decimal places.

• 1.90

• 1.89

• 1.899

• 1.99

A population has a standard deviation of σ = 17.3. How large of a sample must be drawn so that a 95% confidence interval for µ will have a Margin of Error equal to 1.4?

• 586.6

• 587

• 586

• 585

The lifetime of a certain type of batter is known to be normally distributed with a standard deviation of 20 hours. A sample of 50 batteries had a mean lifetime of 120.1 hours. It is desired to construct a 99% confidence interval for the mean lifetime of this type of battery.

What is the Confidence Interval to one decimal place?

• (114.5, 125.6)

• (112.8, 127.4)

• (112.82, 127.38)

• (114.56, 125.64)

You are given two sets of data measuring the same information, both with the same sample size. Set A has a larger Standard Error than Set B. If you were looking for a 99.8% Confidence Interval, which set would have a larger Margin of Error?

• Set A

• Set B

• Not enough information

• I have no idea what you're asking me to do

A person selects a random sample of 15 credit cards and determines the annual interest rate, in percent, of each one. The sample mean is 12.42 with a sample standard deviation of 1.3. It is desired to construct a 90% Confidence Interval.

Find the Standard Error to three decimal places.

• 0.336

• 0.33566

• 13.156

• 0.087

Which of the following is an example of an interval estimate?

• point estimate 

• critical value

• confidence interval

• statistic

A __________ gives an interval of plausible values for the _____________. 

• confidence interval, statistic

• point estimate, parameter

• point estimate, statistic

• confidence interval, parameter

Complete the equation: 
point estimate +/- _____

• standard deviation

• margin of error

• critical value

• confidence level