Measures of Dispersion

• variation/variability/dispersion/spread

• completes description of a distribution: mean/level, shape, and spread

• range - for ordinal and interval scale variables

• IQR (interquartile range)

• box plot: alternate version - whiskers extend to minimum/maximum values

• variance (var.)

• standard deviation (s.d.)

 
 

• outliers: > 2 s.d. from mean