Week 4 Lecture for GM533

1. GM533 Applied Managerial
Statistics Week 4
B. Heard
http://www.facebook.com/statcave

2. 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.

3. Week 4 GM533
• Finding a z-based confidence interval for a
Population Mean Sigma Known

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

5. Week 4 GM533

6. Week 4 GM533
• Finding a t Based Confidence Interval for a
Population Mean Sigma Unknown

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

8. Week 4 GM533

9. Week 4 GM533
• Determining the sample size for a Confidence
Interval µ – σ Unknown

10. 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

11. 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!)

12. Week 4 GM533
• Determining a Large Sample Confidence
Interval for a Population Proportion p

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

14. Week 4 GM533

15. Week 4 GM533
• Determining the Sample Size for a Confidence
Interval for p

16. Week 4 GM533
• First use table, then p = 0.5 when you don’t know
(they told us to), then use equation
Confidence z n ≥ p(1-p)(z/E)^2
90% 1.645 n ≥ 0.5(1-0.5)(1.96/0.03)^2
95% 1.96
98% 2.33
99% 2.58 n ≥ 1067.11
Or 1068 (always round
sample size UP)
Actually always round up!

17. Week 4 GM533
• I will post these in my statcave at
www.facebook.com/statcave