Describing data


discrete variable
continuous variable

Variables may also be classified according to the scale on which they are measured. Scales help us understand the precision of an individual variable and are used to make choices about data visualizations as well as methods of analysis.

A nominal scale describes a variable with a limited number of different values that cannot be ordered.

An ordinal scale describes a variable whose values can be ordered or ranked. As with the nominal scale, values are assigned to a fixed number of categories.

An interval scale describes values where the interval between values can be compared.

A ratio scale describes variables where both intervals between values and ratios of values can be compared.

the mode, the median, and the mean


the frequency distribution also plays a role in selecting which data analysis approaches to adopt.

  • Bar Charts and Frequency Histograms
  • Range
  • Quartiles
  • Box Plots
  • Variance
  • Standard Deviation
  • Shape
    • Lack of Symmetry or Skewness
  • standard error

In addition to the symmetry of the distribution, the type of peak the distribution has should be considered and it can be characterized by a measurement called kurtosis.