Confidence Interval Margin of Error

For a class project, a student in a statistics class surveys the monthly rent for 32 unfurnished one-bedroom apartments in Boston and finds the mean monthly rent to be $1400 with a standard deviation of $220. Find the margin of error for the sample mean. (assuming 95% confidence) Round to the nearest hundredth

• $77.78

• $4.31

• $188.78

• $494.97

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

• 1.65

• 1.96

• 2.58

• 2.33

Which z-value is used for a 90% confidence interval?

• 1.645

• 1.96

• 2.58

• 2.33

Which of the following equation is the correct one for finding the confidence interval?

• a

• b

• c

• d

A sample size of n = 64 is drawn from a population whose standard deviation is σ = 5.6.

Find the margin of error for a 99% confidence interval for µ.

• 1.799

• 1.798

• 1.803

The National Honor Society at Central High School plans to sample a random group of 100 seniors from all high schools in the state to determine the average number of hours per week spent on homework. A 95 percent confidence interval for the mean number of hours spent on homework will then be constructed using the sample data. Before selecting the sample, the National Honor Society decides that it wants to decrease the margin of error. Which of the following is the best way to decrease the margin of error?

• Increase the confidence level to 99%

• Use the population standard deviation

• Use the sample standard deviation

• Decrease the sample size

• Increase the sample size

How do you calculate the margin of error for a 95% confidence interval?

• Multiply the standard deviation by 1.96 and divide by the square root of the sample size.

• Divide the standard deviation by 1.96 and multiply by the square root of the sample size.

• Multiply the standard deviation by the square root of the sample size.

• Divide the standard deviation by the square root of the sample size.

The amount added and subtracted to the statistic.

• Margin of Error

• Point Estimator

• Statistic

• Population

A quality control inspector will measure the salt content (in milligrams) in a random sample of bags of potato chips from an hour of production. Which of the following would result in the smallest margin of error in estimating the mean salt content μ?

• 90% confidence; n = 25

• 90% confidence; n = 50

• 95% confidence; n = 25

• 95% confidence; n = 50

• n=100 at any confidence level

A recent survey of 2000 high schoolers found that 80% use their phones more than 4 hours a day on average. What is the interval for which we could expect to find the truth of the population?

• 2%

• 78% - 82%

• 93% - 97%

• 82%