Unit 7B Confidence Intervals

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

• statistic

• parameter

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

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].

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.

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

• 1.65

• 1.96

• 2.58

• 2.33

T/F Does the statement correctly interpret a 95% confidence interval?

We are 95% confident the true proportion of context is between ___ and ___.

• True

• False

T/F Does the statement correctly interpret a 95% confidence interval?

We are confident, 95% of the intervals would fall in this range.

• True

• False

T/F Does the statement correctly interpret a 95% confidence interval?

If the sampling process were repeated 95% of the answers would lie within the interval.

• True

• False