Ch.9 Estimation & Confidence Intervals

Question 1

3 Assumptions for Confidence Interval

Answer 1

1. Simple Random Sample
2. Sigma is known
3. Normal Distribution or n 30

Question 2

3 Forms of E
Margin of Error

Answer 2

1. σ known
   E=z·σ/sqrt(n)
2. σ unknown
   E=t·s/sqrt(n)
3. Proportion
   E=z·sqrt(pₕₐₜ·qₕₐₜ/n)

Question 3

3 Forms of n # of samples to find

Answer 3

1. σ known
   n=(z·σ/E)²
2. σ unknown
   n=(t·s/E)²
3. Proportion
   n=pₕₐₜ·qₕₐₜ(z/E)²

Question 4

Estimate
1. Confidence Interval
given Cl
2. # of Samples
given Cl & E

Answer 4

1. CL area ⇒ find z or t (df=n-1) ⇒ find E ⇒
   xᵦₐᵣ -E<µ<xᵦₐᵣ+E
2. CL area ⇒ find z or t (df=n-1) ⇒ find n