chapter 3 unit c e280

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chapter 3 unit c e280
2015-05-30 17:47:32
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  1. Arithmetic mean
    • is a primary measure of central location (Average)
    • the mean is sensitive to outliers
  2. median (when outlier affect the mean , median can better indicator of the center of the data)
    • is another measure of central location
    • when data are arranged in ascending order. the median is: the middle value is the number of observations is odd or the average of the two middle values if the number of observation is even
  3. mode
    most frequently occurring value in a data set, a data set can have no modeĀ  one mode of many modes
  4. five number summary
    • S=smallest value=min
    • Q1=1 quartile=25 percentile
    • Q2=median=50 th
    • Q3=3 quartile=75 percentile
    • L=largest=max
  5. range
    inter-quartile range
    • range= Largest-smallest=the number of units within which all of the data exist
    • inter-quartile range =Q3-Q1=the number of units within which the middle 50 % of data exist
  6. box and whisker plot
    you graphically display information from the 5 number summary
  7. Mean Absolute Deviation (MAD)
    is an average of the absolute difference of each observation from the mean
  8. Variance and standard deviation
    the most commonly used measures of dispersion
  9. Coefficient of variation (cv)
    • cv adjust for differences in the magnitudes of the means
    • cv is unitless, allowing easy comparisons of mean-adjusted dispersion across different data sets
  10. Chebyshev's theorem
    • for anydata set, the proportion of observations that lie within k standard deviations from the mean is at least 1-a/k2,where k is any number greater than 1
    • applies to all data sets
    • for k=2 standard dev 75%
    • for k=3 standard dev 89%
  11. the Empirical Rule
    • applies to data sets that are relatively symmetric and bell-shaped
    • 1 standard dev = 68%
    • 2 standard dev =95%
    • 3 standard dev = 99.7 %
  12. Covariance
    describes the direction of the linear relationship between two variables
  13. correlation coefficient
    • describes both the direction and strength of the relationship between x and y
    • closer -1, stronger negative linear
    • closer to+1. stronger positive linear
    • closer to 0, the weaker the linear relationship