Random distribution of numbers to create Bell curve

**squiggler47** · 11-01-2010, 05:44 AM

I think its too early in the morning or I have just worn my brain out with information over the last 2 weeks!

Anyway, I figured I would differ this one to the group for a simple solution!

I want to simulate a bell curve with random numbers for test data, so I need a formula to return a large percentage of numbers around a mid point and get less and less to the outside, with a very marginal ammount of really wild outside points!

=LOOKUP(RAND(),{0.05,0.15,0.5,0.85,0.95},{0.03,0.02,0.01,0.01,0.02,0.03})*RAND()+MIDPOINT-RANGE

was where I was looking

**Andy Pope** · 11-01-2010, 05:49 AM

Does this help
http://support.microsoft.com/default...b;en-us;213930

**squiggler47** · 11-01-2010, 07:12 AM

Not really, the problem I have is I am designing a spreadsheet based on a bell curve, I have my graphs and controls (this is a process sigma dashboard).

The problem is I want to generate some random data, to verify that the charts are working, which I have in my original, but I used fixed formulas to generate a data set of 100, which looks quite nice on the histogram, but isnt a perfect bell curve (i dont want perfect) I just want to generate a larger data set of variable length!

**Andy Pope** · 11-01-2010, 07:17 AM

The article says,

In the following example you can create a bell curve of data generated by Excel using the Random Number Generation tool in the Analysis ToolPak. After Microsoft Excel generates a set of random numbers, you can create a histogram using those random numbers and the Histogram tool from the Analysis ToolPak. From the histogram, you can create a chart to represent a bell curve.

Randon data, histogram and bell curve. Looks like a pretty good fit to me.

**squiggler47** · 11-01-2010, 07:58 AM

Sorry Andy, you are of course quite correct!

I have been pounding my head with statistics and maths all week and I think it just gave out, nothing is going in any more!

Still it seems a little strange generating random numbers based on a normal and standard deviation, so I can calculate the normal and standard deviation! Still at least I know what they are before I start, so I can check my results!

**squiggler47** · 11-20-2010, 06:10 PM

as an addendum :-

=NORMINV(RAND(),Rand_Mean,Rand_Std_Dev)

Creates random numbers for a bell curve given the Mean of the numbers required and the Standard deviation. I used this to get a changing set of data to test my sheet!

**jkf943** · 05-10-2013, 12:41 PM

I'm having the same problem. But this article does not help in 2010 because MS decided to take away all the basic functionality and impose the Ribbon on users. I just want to use random data. I'm going to resort to crayons soon/

I can't get past the following because I don't know what the alternative is without the Tools menu:

"On the Tools menu, click Data Analysis.
In the Analysis Tools box, click Random Number Generation, and then click OK.
In the Number of Variables box, type 1.
In the Number of Random Numbers box, type 2000."

**arlu1201** · 05-13-2013, 09:39 AM

jkf,

Unfortunately you need to post your question in a new thread, it's against the forum rules to post a question in the thread of another user. If you create your own thread, any advice will be tailored to your situation so you should include a description of what you've done and are trying to do. Also, if you feel that this thread is particularly relevant to what you are trying to do, you can surely include a link to it in your new thread.