Chapter Six Normal Curves and Sampling Probability Distributions - PowerPoint PPT Presentation

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Chapter Six Normal Curves and Sampling Probability Distributions

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  1. Chapter SixNormal Curves and Sampling Probability Distributions

  2. Chapter 6 Section 2 Standard Units and Areas Under the Standard Normal Distribution

  3. Z Score • The z value or z score tells the number of standard deviations the original measurement is from the mean. • The z value is in standard units.

  4. Formula for z score

  5. Calculating z-scores The amount of time it takes for a pizza delivery is approximately normally distributed with a mean of 25 minutes and a standard deviation of 2 minutes. Convert 21 minutes to a z-score.

  6. Calculating z-scores Mean delivery time = 25 minutes Standard deviation = 2 minutes Convert 29.7 minutes to a z score.

  7. Interpreting z-scores Mean delivery time = 25 minutes Standard deviation = 2 minutes Interpret a z score of 1.6. The delivery time is 28.2 minutes.

  8. Standard Normal Distribution: μ = 0 σ = 1 Values are converted to z scores where

  9. Importance of the Standard Normal Distribution: Standard Normal Distribution: 1 0 Any Normal Distribution: The areas are equal. μ 1σ

  10. Use of the Normal Probability Table (Table 4) - Appendix I Entries give the probability that a standard normally distributed random variable will assume a value between the mean (zero) and a given z-score.

  11. To find the area betweenz = 0 and z = 1.34

  12. Patterns for Finding Areas Under the Standard Normal Curve To find the area between a given z value and zero: Use Table 4 (Appendix I) directly. z 0

  13. Patterns for Finding Areas Under the Standard Normal Curve To find the area between z values on either side of zero: Add area from z1 to zero toarea from zero to z2 . z1 z2 0

  14. Patterns for Finding Areas Under the Standard Normal Curve To find the area between z values on the same side of zero: Subtract area from zero to z1 from the area from zero to z2. z1 z2 0

  15. Patterns for Finding Areas Under the Standard Normal Curve To find the area to the right of a positive z value or to the left of a negative z value: Subtract the area from zero to z from 0.5000 . 0.5000 z 0

  16. Patterns for Finding Areas Under the Standard Normal Curve To find the area to the left of a positive z value or to the right of a negative z value: Add 0.5000 to the area from zero to z . 0.5000 table z 0

  17. Use of the Normal Probability Table a. P(0 < z < 1.24) = _________________ b. P(0 < z < 1.60) = _________________ c. P( - 2.37 < z < 0) = ________________ 0.3925 0.4452 0.4911

  18. Normal Probability 0.9974 d. P( - 3 < z < 3 ) = ____________________ e. P( - 2.34 < z < 1.57 ) = ______________ f. P( 1.24 < z < 1.88 ) = ________________ g. P(-3.52<z< -0.98) = __________________ 0.9322 0.0774 0.1633

  19. Normal Probability 0.9495 h. P(z < 1.64) = _________________ i. P(z > 2.39) = __________________ j. P(z > -1.35) = _________________ k. P(z < -0.64) = _________________ 0.0084 0.9115 0.2611

  20. Application of theNormal Curve The amount of time it takes for a pizza delivery is approximately normally distributed with a mean of 25 minutes and a standard deviation of 2 minutes. If you order a pizza, find the probability that the delivery time will be:a. between 25 and 27 minutes. a. ____________ b. less than 30 minutes. b. ____________ c. less than 22.7 minutes. c. ____________ 0.3413 0.9938 0.1251

  21. Application of theNormal Curve The amount of time it takes for a pizza delivery is approximately normally distributed with a mean of 25 minutes and a standard deviation of 2 minutes. If you order a pizza, find the probability that the delivery time will be:a. between 25 and 27 minutes. 0.3413 0 1

  22. Application of theNormal Curve The amount of time it takes for a pizza delivery is approximately normally distributed with a mean of 25 minutes and a standard deviation of 2 minutes. If you order a pizza, find the probability that the delivery time will be:b. less than 30 minutes. 0.9938 2.5

  23. Application of theNormal Curve The amount of time it takes for a pizza delivery is approximately normally distributed with a mean of 25 minutes and a standard deviation of 2 minutes. If you order a pizza, find the probability that the delivery time will be: c. less than 22.7 minutes. 0.1251 -1.15

  24. Homework Assignments Chapter 6 Section 2 Pages 274 - 276 Exercises: 1 - 49, odd Exercises: 2 - 50, even