A Note on Box and Whisker Plots

The box and whisker plot will summarize each variable by three components:

  1. A central line to indicate central tendency or location;
  2. A box to indicate variability around this central tendency;
  3. Whiskers around the box to indicate the range of the variable.

After clicking the Box and Whisker button (see the

Advanced

tab of the Review DescriptiveStatistics dialog box), you can choose to plot for each variable:

  • Medians (central line), quartiles (box), and ranges (whiskers); note that the specific method that is used to compute medians and quartiles can be configured via the Computation of percentiles box in the Options dialog box - Analyses/Graphs: Limits tab. For more information, see Percentile Calculation Options in  Statistica.
  • Means, standard errors of the means, and standard deviations;
  • Means, standard deviations, and 1.96 times the standard deviations (95% normal confidence interval for individual observations around the mean);
  • Means standard errors of the means, and 1.96 times the standard errors of the means (95% normal confidence interval for means).