Confidence Intervals and Sample Size

Margin of Error is equal to:

• Standard Deviation

• 2 * Standard Deviation

• Critical Value

• Point Estimate

True or False: The more confident you want to be, the smaller your confidence interval will be.

• True

• False

Which of the following changes to a study would result in a smaller confidence interval?

• increasing the confidence level, increasing the sample size

• increasing the confidence level, decreasing the sample size

• decreasing the confidence level, decreasing the sample size

• decreasing the confidence level, increasing the sample size.

Which z-value is used for a 95% confidence interval?

• 2.58

• 1.66

• 1.96

• 2.33

The amount added and subtracted to the statistic.

• Margin of Error

• Confidence Interval

• Z Score

• Population

What is the margin of error for the interval (6.8, 12.9)?

• 9.85

• 3.05

• 3.50

• 6.8

The height of women is normally distributed with an average height of 64 inches and a standard deviation of 2.5 inches. What interval contains 99.7% of all data?

• 61.5 to 66.5

• 56.5 to 71.5

• 59 to 69

• 2.5 to 99.7

Identify the confidence interval used in the figure below if each shaded area is equal to 0.05.

• 90%

• 95%

• 97%

• 99%

A research company wants to estimate the proportion of people who like oatmeal. They want the confidence level to be 95%. The company gets 325 people to sign up for the survey, but on the day that the survey is issued, only 250 people show up and take the survey. What happens to the confidence interval?

• It stays the same

• It gets smaller

• It gets larger

• Not enough information

A recent study of 750 Internet users in Europe found that 35% of Internet users were women. What is the 95% confidence interval of the true proportion of women in Europe who use the Internet?

• 0.321 < p < 0.379

• 0.316 < p < 0.384

• 0.309 < p < 0.391

• 0.305 < p < 0.395