Interpreting Confidence Intervals

When interpreting the confidence interval, make sure that you are describing the 

• statistic
• parameter

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

Suppose that $51,759 was the median income for all households in 2012. Does the interval ($51,484, $52,394) provide convincing evidence that the median household income increased in 2013? 

• Yes
• No

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].

Is there bias? 
A four company wants to know what percent of local households bake at least twice a week. A company representative calls 500 randomly selected households during the daytime. 

• Yes
• No

Increasing the sample size __________ the confidence interval. 

• increases
• decreases
• does not affect
• there is not enough evidence to determine the answer

What can you do to reduce the margin of error? 

• increase the confidence level
• decrease the confidence level
• increase sample size
• decrease sample size

Are the conditions met? 
A recent poll of 738 randomly selected customers of a major US cell-phone carrier found that 170 of them had walked into something or someone while talking on a cell phone. 

• Yes
• No
• There is not enough data to determine.