Also called “measure of variability or spread”

  • range – difference between the highest and lowest values + often both extremes are reported with it
  • interquartile range – alternative measure, less influenced by extreme values = range of the middle 50% of values in data set – calculated as the difference between 75th and 25th percentile values
  • variance + standard deviation – both describe how much are the individual values in a data set different from the mean (average)
    • variance – averageĀ  of the squared deviations from the mean
    • standard deviation – square root of the variance
  • outliers – data points or observations which are quite different from other in data sets