Confidence interval, margin of error, sample size

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

Which of the following equation is the correct one for finding the margin of error?

• a

• b

• c

• d

What is the X with an overline stands for?

• mean or average

• Z-score

• Standard deviation

• Sample size

What is the S in this equation?

• mean or average

• Z-score

• Standard deviation

• Sample size

What is the n in this equation?

• mean or average

• Z-score

• Standard deviation

• Sample size

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

In a crash test of 15 troopers, collision repair costs are found to have a distribution that is approximately normal, with a mean of $1800 and a sample standard deviation of $950. Construct a 99% confidence interval for the repair cost. 

• (1069.77, 2530.23)

• (1077.13, 2522.87)

• (1167.15, 2432.85)

• None of these.

A sample of 40 people owned an average of 1.35 apple products. It is known from a previous study that the population standard deviation of apple product ownership is 0.63 products. Construct a 95% confidence interval.

• (1.11, 1.58)
• (1.15, 1.55)
• (1.19, 1.51)
• (1.09, 1.61)