Confidence Intervals (unknown σ)

What is the formula for the margin of error "E" for a t-distribution (σ unknown):

In a t-distribution, the mean, median, and mode are all zero.

• True

• False

The tails of a t-distribution are narrower than those of the normal distribution.

• True

• False

 As the degrees of freedom decrease, the shape of the t-distribution approaches the normal distribution.

• True

• False

If a set of data has a sample size of 18, then the degrees of freedom for the t-distribution is d.f. = 18.

• True

• False

When constructing a confidence interval for a t-distribution (σ unknown), the data must be normally distributed, or n ≥ 30

• True

• False

Given a sample standard deviation "0.5", n=30, and a confidence interval "90%". Solve for the margin of error "E" for the t-distribution (σ unknown). Round your answer to the nearest hundredth.

• 0.16

• 1.18

• 0.19

• 1.06

Given a sample standard deviation "2", n=100, and a confidence interval "95%". What is the degree of freedom?

• 100

• 99

• 98

• 95

Given a sample standard deviation "5", n=100, and a confidence interval "99%". Solve for the margin of error "E" for the t-distribution (σ unknown). Round your answer to the nearest hundredth.

• 1.31

• 0.85

• 0.99

• 1.21

Given a sample standard deviation "0.5", n=30, and a confidence interval "99%". what is the critical value for the t-distribution (σ unknown). Round your answer to the nearest hundredth.

• 2.626

• 2.756

• 2.750

• 2.763