Normal curve tail area
0. Quick guide - background
In this module:
- Construct a chart of the normal distribution density function - using area charts (Fig 1.①)
- Compare the tail area color for fine and coarse step sizes (Fig 1.②)
- Perform a visual comparison to the Peltier (2013) version with its XY-area chart combination plus date axis (Fig 1.③)
1. Normal tail area
Circle numbers refer to image components in figure 1.
xlf :: combo area - area :: step 0.1
- Worksheet: N(0, 1) #2
- z value: cell U7: -3.5
- Formula: cell V7:
=NORM.S.DIST(U7,FALSE)
- z step: 0.1
- Chart type: Combo - Area and Area
The coarse step increment causes the left margin of the blue tail area to slope (1.5 at the base to 1.6 at the peak).
xlf :: combo area - area :: step 0.01
- Worksheet: N(0, 1) #2
- z value: cell B7: -3.5
- Formula: cell C7:
=NORM.S.DIST(B7,FALSE)
- z step: 0.01
- Chart type: Combo - Area and Area
The finer step increment (0.01) returns a left margin of the blue tail area that visually appears to be vertical.
Peltier :: combo area - XY with smoothed lines :: step [modified date]
Peltier (2013) uses includes an XY type chart with secondary axis and X values treated as dates.
- Worksheet: Peltier #1
- Chart type: Combo - Area and XY
See Peltier (2013) for details.

2. Discussion
An examination of figure 1, items 2 and 3 suggests that the area plot with fine increments is equivalent to the Peltier XY plot, at least for a tail area.
References
- Peltier Tech Blog (2013), Fill Under a Plotted Line: The Standard Normal Curve, accessed 12 September 2019
- Microsoft (2018) XL: How to Create a Bell Curve Chart, accessed 12 September 2019
- Download the Excel file for this module: xlf-norm-dist-chart-1.xlsx [103 KB]
- Development platform: Office 365 ProPlus Excel 64 bit.
- Published: 14th September 2019
- Revised: Friday 24th of February 2023 - 03:12 PM, Pacific Time (PT)