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