Chapter 12

Question 1

Interpreting a CI of a Mean

Answer 1

You are 95% sure that the
95% CI includes the
population mean.
• By convention write like:
• 36.75 to 36.89
• or [36.75, 36.89]
• Not like “36.75-36.89”

Question 2

Sample mean:

Answer 2

this is our
best estimate of the
population mean.

Question 3

SD (s):

Answer 3

as SD increases, the

CI increases proportionally

Question 4

Sample size:

Answer 4

the CI is
inversely proportional to
the square root of the
sample size.
• If the sample were 4 times larger,
then the CI would be half as wide.

Question 5

Degree of confidence:

Answer 5

you can generate a narrower
interval with lower degree of confidence.
• Wide: 90%, Wider: 95%, Even Wider: 99%

Question 6

Assumptions: CI of a Mean

Answer 6

New one:
• The true population is at least approximately
Gaussian.
• Stay tuned for bootstraps and permutations that
don’t assume this.

Question 7

df =

Answer 7

n - 1

Question 8

How to Calculate the

CI of a Mean

Answer 8

W = (tcrit * s) / √n