Statistics Ch 2

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  1. Measures of center
    mean & median
  2. Mean
    • symmetrical distribution, arithmetic average, influenced by skew and outliers
    • For symmetrical distribution, the mean and median will be the same
  3. Median
    skewed distribution , midpoint of a distribution, resistant to skew and outliers

    For skewed distribution, the mean is influenced by extreme observations
  4. Measures of spread
    Quartiles & Standard Deviation
  5. Quartiles
    skewed distribution
  6. First Quartile
    value in the sample that has 25% of the data at or below it
  7. Third Quartile
    value in the sample that has 75% of the data at or below it
  8. Interquartile range
    (IQR) = Q3 - Q1
  9. Outlier
    an individual value that falls outside the overall pattern.
  10. Low outlier:
    any value < (Q1 – 1.5 IQR)
  11. High outlier
    any value > (Q3 + 1.5 IQR)
  12. Standard Deviation
    • (s) – symmetrical distribution
    • Variation around the mean, how spread out from the mean the data is
    • When s = 0 : no spread in the data
    • As s increases, the data is more widely spread around the mean
  13. Statistical Summary
    Symmetrical distribution & Skewed distribution
  14. Symmetrical distribution
    mean and standard deviation
  15. Skewed distribution
    • five number summary, boxplot
    • [Minimum, Q1, M, Q3, Maximum]
Card Set:
Statistics Ch 2
2012-02-26 00:10:36

Describing Distributions with Numbers Shape, spread, center
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