Probability and Stats 7.1: Idea of Confidence Interval

Polling organizations regularly survey US adults to ask if they approve of the job the president is doing. on the day of the 2014 midterm elections, the 95% confidence interval for the proportion of all US adults that approved of President Obama's job performance was 0.39 to 0.45. Interpret the confidence interval.

• The probability that the true proportion of all US adults that approve of Obama's job performance is between 0.39 to 0.45.

• The probability that the true proportion of all US adults that approve of Obama's job performance is 95%.

• We are 95% confident that the interval from 0.39 to 0.45 captures the true proportion of all US adults who approve of Obama's job performance.

• We are 95% confident that the interval from 0.39 to 0.45 captures the sample proportion of all US adults who approve of Obama's job performance.

Polling organizations regularly survey US adults to ask if they approve of the job the president is doing. on the day of the 2014 midterm elections, the 95% confidence interval for the proportion of all US adults that approved of President Obama's job performance was 0.39 to 0.45. Calculate the point estimate.

• 0.39

• 0.45

• 0.42

• 0.06

• 0.03

Polling organizations regularly survey US adults to ask if they approve of the job the president is doing. on the day of the 2014 midterm elections, the 95% confidence interval for the proportion of all US adults that approved of President Obama's job performance was 0.39 to 0.45. Calculate the margin of error.

• 0.39

• 0.45

• 0.42

• 0.06

• 0.03

Polling organizations regularly survey US adults to ask if they approve of the job the president is doing. on the day of the 2014 midterm elections, the 95% confidence interval for the proportion of all US adults that approved of President Obama's job performance was 0.39 to 0.45.

Based on the confidence interval, it is plausible that on the day of the 2014 midterm elections, a majority of US adults approved of Obama's job performance.

• True

• False

A local pizza shop claims that they deliver pizzas in under 30 minutes on average. You randomly select 12 different times during the next week and order a pizza to be delivered to your home. The 95% confidence interval for the mean delivery time is 26.8 minutes to 41.0 minutes. Interpret the confidence interval.

• The probability that the true mean delivery time is 30 minutes is 95%.

• The probability is 95% that the true true mean delivery time is between 26.8 and 41 minutes.

• We are 95% confident that the interval from 26.8 to 41 minutes captures the sample mean delivery time.

• We are 95% confident that the interval from 26.8 to 41 minutes captures the true mean delivery time.

A local pizza shop claims that they deliver pizzas in under 30 minutes on average. You randomly select 12 different times during the next week and order a pizza to be delivered to your home. The 95% confidence interval for the mean delivery time is 26.8 minutes to 41.0 minutes. Calculate the point estimate.

A local pizza shop claims that they deliver pizzas in under 30 minutes on average. You randomly select 12 different times during the next week and order a pizza to be delivered to your home. The 95% confidence interval for the mean delivery time is 26.8 minutes to 41.0 minutes. Calculate the margin of error

A local pizza shop claims that they deliver pizzas in under 30 minutes on average. You randomly select 12 different times during the next week and order a pizza to be delivered to your home. The 95% confidence interval for the mean delivery time is 26.8 minutes to 41.0 minutes.

According to the confidence interval, is the local pizza shop's claim correct?

• Yes

• No