Great question! Since GSTG22 doesn’t have a specific section addressing bell curves or normal distribution graphs, we have to interpret the existing guidance and apply it to this type of graphic. While the distribution graph itself is not a number line, it does contain a number line, so the guidance for number lines applies to that portion of the graphic.
Follow the guidance in Unit 6.5, Number Lines. The number line should be transcribed according to the guidelines and standards in Unit 6, Diagrams for Technical Material, specifically 6.5.1.
6.5.1 Number Lines: “All number lines transcribed in Nemeth within UEB contexts must be enclosed within Nemeth Code switch indicators even though numbers may not be modified.”
6.5.1.1: “A numeric indicator is not used before a number if it occurs below the number line, whether the number is whole, fractional, decimal, or negative. Follow these guidelines for the numeric indicator regardless of whether the number line is transcribed in UEB or Nemeth Code.”
See also: The chart in Unit 6, page 6-3, “Use and Omission of Numeric Indicator.”
Based on this guidance, we treat the number line portion of the normal distribution graph as a number line and apply the corresponding numeric indicator rules.