GM533 Applied Managerial Statistics Week 4

B. Heardhttp://www.facebook.com/statcave

Week 4 GM533

• These are considered practice problems, thus I’m going to walk you through them.

• Do these on your own and verify your answers.

Week 4 GM533

• Finding a z-based confidence interval for a Population Mean Sigma Known

Week 4 GM533• In Minitab• Stat >> Basic Statistics >> 1 sample z

Week 4 GM533

Week 4 GM533

• Finding a t Based Confidence Interval for a Population Mean Sigma Unknown

Week 4 GM533• In Minitab• Stat >> Basic Statistics >> 1 sample t

Week 4 GM533

Week 4 GM533

• Determining the sample size for a Confidence Interval µ – σ Unknown

Week 4 GM533• In Mintab• Calc >> Probability Distributions >> t (Choose Inverse Cumulative Probability)

Degrees of freedom is sample size – 1 or 20 – 1 = 19

Input constant is the Confidence + (1-confidence)/2)Or 95% + (1-95%)/2 = 97.5% or 0.975

Week 4 GM533

• Input into equation

n = (s*t/E)^2

n = (25*2.093/5)^2

n = 109.5

n = 110(Always round sample sizes up!)

Week 4 GM533

• Determining a Large Sample Confidence Interval for a Population Proportion p

Week 4 GM533• In Minitab• Stat >> Basic Statistics >> 1 Proportion

Week 4 GM533

Week 4 GM533

• Determining the Sample Size for a Confidence Interval for p

Week 4 GM533

• First use table, then p = 0.5 when you don’t know (they told us to), then use equation

Confidence z90% 1.64595% 1.9698% 2.3399% 2.58

n ≥ p(1-p)(z/E)^2n ≥ 0.5(1-0.5)(1.96/0.03)^2

n ≥ 1067.11

Or 1068 (always round sample size UP)

Actually always round up!

Week 4 GM533

• I will post these in my statcave atwww.facebook.com/statcave