[Statistics 101] (5) Descriptive and Inferential

The characteristics of a data set are called “Descriptive Statistics.” And the estimation of population’s characteristics using descriptive statistics are called “Inferential Statistics”.

Descriptive Statistics

• Mean, variance, standard deviation
• Max and Min

• Variance
  • How spread out the data are
• Skewness
  • How symmetrically the data are distributed
    • 0: Symmetric
    • positive (>0): Skewed to the right (the right tail is longer)
    • negative (<0): Skewed to the left (the left tail is longer)

• Kurtosis
  • A measure of whether the data are peaked or flat relative to a normal distribution.
  • Data sets with high kurtosis tend to have a distinct peak near the mean, decline rather rapidly.
  • Data sets with low kurtosis tend to have a flat top near the mean.
  • Leptokuritc: positive kurtosis
  • Platykurtic: negative kurtosis
  • Mesokurtic: 0