Excel 2020: Create a Bell Curve in Excel
March 23, 2020  by Bill Jelen
I have 2200 Excel videos on YouTube. I can never predict which ones will be popular. Many videos hover around 2,000 views. But for some reason, the Bell Curve video collected half a million views. I am not sure why people need to create bell curves, but here are the steps.
A bell curve is defined by an average and a standard deviation. In statistics, 68% of the population will fall within one standard deviation of the mean. 95% falls within two standard deviations of the mean. 99.73% will fall within three standard deviations of the mean.
Say that you want to plot a bell curve that goes from 100 to 200 with the peak at 150. Use 150 as the mean. Since most of the results will fall within 3 standard deviations of the mean, you would use a standard deviation of 50/3 or 16.667.
 Type
150
in cell B1.  Type
=50/3
in cell B2.  Type headings of Point, X, Y in cells A4:C4.

Fill the numbers 1 to 61 in A5:A65. This is enough points to create a smooth curve.
 Go to the midpoint of the data, point 31 in B35. Type a formula there of
=B1
to have the mean there.  The formula for B36 is
=B35+($B$2/10)
. Copy that formula from row 36 down to row 65. 
The formula for B34 is
=B35($B$2/10)
. Copy that formula up to row 5. Note that the notes in columns C:E of this figure do not get entered in your workbook  they are here to add meaning to the figure.The magic function is called NORM.DIST which stands for Normal Distribution. When statisticians talk about a bell curve, they are talking about a normal distribution. To continue the current example, you want a bell curve from 100 to 200. The numbers 100 to 200 go along the Xaxis (the horizontal axis) of the chart. For each point, you need to calculate the height of the curve along the yaxis. NORM.DIST will do this for you. There are four required arguments:
=NORM.DIST(This x point, Mean, Standard Deviation, False)
. The last False says that you want a bell curve and not a Scurve. (The SCurve shows accumulated probability instead of point probability.) 
Type
=NORM.DIST(B5,$B$1,$B$2,False)
in C5 and copy down to row 65. 
Select B4:C65. On the Insert tab, open the XYScatter dropdown menu and choose the thumbnail with a smooth line. Alternatively, choose Recommened Charts and the first option for a bell curve.
The result: a bell curve, as shown here.
Title Photo: Chris Barbalis at Unsplash.com
This article is an excerpt from MrExcel 2020  Seeing Excel Clearly.