Chapter 22: Confidence Intervals for a Mean

Question 1

TInterval & TTest Conditions

Answer 1

1. Random sample
2. n≤10% of pop.
3. n≥30 (CLT) or no strong skewness or outliers

Question 2

t Distributions

Answer 2

1. Mean = 0
2. Variability is determined by degrees of freedom (df=n-1)
3. Shape similar to normal distribution, but with fatter tails and slightly lower peak
4. As degrees of freedom increase, the tails get thinner and the peak gets higher
5. t*=InvT([1-c]/2,df)

Question 3

TInterval On Calculator

Answer 3

(Data and input into lists if no mean and SD given)
Stats
x̄: sample mean
Sx: sample SD
n: sample size
C-Level: CI% as decimal

Question 4

TTest p-value Interpretation

Answer 4

“Assuming [H0 in context] is true, there is a [p-value] probability of getting an x̄ of [x̄] or more extreme purely by chance.”

Question 5

TTest

Answer 5

(Data and input into lists if no mean and SD given)
Stats
μ0: null hypothesis
x̄: sample mean
Sx: sample SD
n: sample size
μ (≠μ0; <μ0; >μ0)