Interpreting Confidence Intervals

Increasing the sample size will:

• A. Increase the width of the confidence interval.

• B. Decrease the width of the confidence interval.

• C. Have no effect on the width of the confidence interval.

• D. Increase the level of confidence.

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

• True

• False

What is the format for interpreting a confidence interval? 

• The interval from ___ to ___ captures the true mean in context.

• C% of samples of the same size taken from the same population will capture the parameter in question

• There is convincing evidence that C% gives the interval (___, ___) capturing the parameter in question.

• We are C% confident that the interval from ___ to ___ captures the [parameter in context].

Complete the equation: 
point estimate +/- _____

• standard deviation

• margin of error

• critical value

• confidence level

The more confident you want to be, the smaller your confidence interval will be.

• True

• False

The larger your confidence interval is, the more sure (higher confidence level) you can be.

• True

• False

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 gets larger

• It gets smaller

• It stays the same

• Too little information given

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 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