Confidence Interval for Proportions

What is the margin of error of this sample?

• 0.28

• 0.14

• 0.342

• 0.684

If 827 represents "no" voters out of 2584, construct a 95% confidence interval for the "no" group.

• [.300,.340]

• [.298,.342]

• [.302,.338]

• [.288,.352]

The symbol for the sample proportion is __________.

• z*

• p̂

• E

• p

Find the value of z* for a 90% confidence interval.

• -1.96

• 1.645

• 1.440

• -1.598

In a survey about the number of people that favor the current mayor resulted in the confidence interval below. A 99% confidence interval for p is (0.652, 0.868). Interpret this interval.

• 99% of the time the true proportion of people who favor the mayor is between 65.2% and 86.6%.

• The probability that the population proportion of people that favor the mayor is between 65.2% and 86.6% is 99%.

• Based on this sample, I am 99% confident that the true proportion of people that favor the mayor is between 65.2% and 86.6%.

In a survey about the number of people that favor the current mayor resulted in the confidence interval below. A 99% confidence interval for p is (0.652, 0.868). Interpret this LEVEL.

• 99% of all intervals using this method will capture the true proportion of people that favor the mayor.

• 99% of the time, the interval will capture the true proportion of people who favor the mayor.

HSHS has about 1432 students this year. A random sample of 100 HSHS students found that 53 of them were in possession of a pencil. What is the point estimate for this sample?

• 0.53

• 50

• 100

• 1432

Which confidence would result in a larger margin of error (assuming nothing else changed), 91% or 97%?

• 97%

• 91%

• They have the same margin of error.

Increasing the sample size makes the confidence interval

• wider.

• narrower.

• does not affect the interval.

Decreasing the confidence level makes the confidence interval

• wider.

• narrower.

• does not affect the interval.