Show:
General Ideas
Assumptions
Applications
Misc (Non QLT)
100

What are we trying to estimate with a confidence interval?

The population average, u

100

What type of sample must we take to use confidence intervals?

A simple random sample

100

When would we use a z interval instead of a t interval?

1. The population standard deviation is known

2. Sample size is large

(The opposite requirements are for the t interval)

100

Definition: Using a sample to infer about an unknown population average.

Inference

200

What is the best estimator of the population average?

The sample average.

200

What can we not have in our sample in order to do a confidence interval?

Outliers

200

What is the last step when calculating a required sample size?

ROUND UP

200

If we created 700 confidence intervals all at 60% confidence level, how many would we expect to not capture the true average?

700 * (100%-60%) = 280

300

What should we do if we want to create a larger margin of error?

1. Decrease the sample size

2. Increase the confidence level

300

For a sample size of 5, what shape must the distribution be?

Bell shape

300

Find the critical value, z* for a 70% confidence interval.

1.0

300

What is the equation for the margin of error?

ME = (z*s/sqrt(n))

400

True or False:

If a guess of the population average is greater than our lower bound and less than our upper bound, we say that it could be correct.

True.

If the guess is inside the confidence interval, it could be correct. 

400

For a sample size of 29, what shape must the distribution be?

Symmetric

400

Find the 60% confidence interval for the following information:

sample average = 6

sample standard deviation = 1

sample size = 50

(5.9, 6.1)

400

What would be the confidence interval with a confidence level of 0%?

(sample average, sample average)
500

What theorem allows us to do confidence intervals?

The central limit theorem [not on QLT]

500

For a sample size of 200, what shape must the distribution be?

Anything

500

True or False:

If we consider all possible 80% confidence intervals arising from all possible samples of the population, then 80% of those intervals should contain the population average.

FALSE

If we consider all possible 80% confidence intervals arising from all possible samples of the same size of the population, then 80% of those intervals should contain the population average.

500

What would be the confidence interval with a confidence level of 100%?

(-infinity,+infinity)