Descriptive and Bivariate Statistics

Descriptive Statistics

  • Standard Deviation (S.D. or o)
    • Average deviation of each observation from precise centre of all weighted observations, but sensitive to relative weights of observations.
      • Indicates how dispersed points are from the mean
      • More precise than mean deviation; preferred.
  • Example:
    • David Demers….
      • N = 198 newspapers
      • M = 2.64 editorials
      • o = +/- 1.84
      • Range = 0 – 8
      • Standard deviation tells us that the amount of editorials/paper is not around 2.64, but between the dispersion of 0.8 and 4.48 (2.64 +/- 1.84)

Bivariate Statistics

  • Analysis of two sets of data
  • Coefficient of Correlation
    • Indicates extent to which ordered pairs of observations share variance
    • It gauges if the behaviours of two phenomena are related.
      • Example
      • If x happens, does y happen?
      • If x happens, how much does y happen?
  • For correlation and scatter points:
    • Ordered pair = two related numbers (x, y)
    • Examples:
      • (x,y) [scatter plot of x and y analysis, use excel]
        • Hours of television, hours of radio
        • Age, hours of television
        • Education (coded?), hours of radio
        • Age, education.
  • Coefficient of correlation or Pearsons r
    • “Coefficient” = measure of strength of correlation expressed as r = + z or – z
      • 0-10 (no correlation)
      • 10-30 (slight degree of relationship)
      • 30-50 (fair degree of relationship)
      • Common knowledge…
  • Descriptive Statistics àCorrelation of Coefficient
    • Can do
      • Flag significant data (e.g. highs, lows, averages)
      • Reveals patterns
      • Suggests relationships between values
      • Indicate strength relationship between two values
    • Can’t do
      • Provide explanations
      • You must provide the explanation

Cool Related Sites:

On SEOMOZ “Knowledge” about Statistics « IR Thoughts
Statistics for Business and Economics « Khmer Campus – for unde..
Language Log » Physiological politics
Data Analysis Part 1: Database Management, Distributions, and Bivariates &l..
A Little Primer on Multicollinearity « DemocraticPeace Blog
Good Government vs. Less Government « The Baseline Scenario