Confidence Intervals and Population Size Review

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

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

You sample 16 students in your school, and they average 13 hours of TV a week. Assume the standard deviation is 3. Find a 99% Confidence Interval.

Which of the following is incorrect?

• μ = 13

• σ = 3

• Z = 1.645

• n = 16

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 narrower

• It gets wider

• Not enough information

A random sample of 100 visitors to a popular theme park spent an average of $142 on the trip with a standard deviation of $47.5. Which of the following would be the 98% confidence interval for the mean money spent by all visitors to this theme park?

• ($130.77, $153.23)

• ($132.77, $151.43)

• ($132.69, $151.31)

• ($140.88, $143.12)

You sample 12 bugs and find the sample mean is 2.40 cm. You are told the standard deviation is 0.2 cm. Find a 95% Confidence Interval.

• 12

• Z

• .2

• n

• 1.96

• μ

• 2.40

• σ

A preliminary study suggests that 17% of people agree on an issue. How large must your sample size be so you could be within ± 5% with 95% confidence?

• 217

• 30

• 385

• 152

We measure the height of 40 randomly selected women, in which the mean height is 175cm. We also know the population standard deviation is 20cm. Which of the following represents a 95% Confidence Interval?

• 175cm ±1.645* 3.16

• 175cm ± 1.96*3.16

• 175cm ± 1.96*20

• 175cm ± 1.645*40