# Plotting a normal distribution

Six Sigma – iSixSigma Forums Old Forums General Plotting a normal distribution

Viewing 10 posts - 1 through 10 (of 10 total)
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• #45286

Siegler
Member

I’m trying to generate a normal plot of a group of excel values. I used the normdist function to do this. However, I get values over 1 when I do this. any tips on where I am going wrong?

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#147550

Lobo
Participant

Try Googling “normal probability plots in excel”

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#147552

Siegler
Member

Google doesn’t answer my question. Is there something specific I am making a mistake with?
I have a list of values for which I want to plot a normal curve with excel. I calculated the mean and stdev for the set and then used normdist to get the p value to plot. I get values over 1 which is obviously not right.

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#147556

Whitehurst
Participant

Theres no function that will draw a normal probability plot in excel.

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#147557

Robert Butler
Participant

I don’t use Excel for my statistics but based on a quick read of the help section for the NORMDIST function it appears the function will generate random numbers from a normal distribution with mean 0 and standard deviation = 1.  If this is in fact what it is doing then you should get values greater than 1 and less than -1.

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#147603

Lee
Participant

I too found no canned function, so I made a spreadsheet that accepts values, plots the histogram, provides statistics, and then overlays the normal curve shape over the histogram of plotted points.  It is just part of a worksheet I use to generate SPC charts.  It is not 100% automated, but it beats nothing.
Contact me offline, at [email protected] if you want to followup.
Eugene

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#147608

Savage
Participant

True there is no canned way to plot a normality plot in Excel – unless you purchase one of the many programs that do this.
Here’s a way to do it though:
Assumptions:  raw data are in column A and you have n data values.
1)  Use the RANK function in column B to rank the raw data (use the help to see how to do this)
2)  Use this expression –>  ((column B-.5)/n)   (this is column C)
3)  Use the NORMINV function with column C as the probaility.  (this will be column D)
4) Create a scatter plot with column A as the x-axis and column D as the y-axis.

Try that and see if that meets your needs.

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#147624

BTDT
Participant

Siegler:Send me a note at 6SigmaGuru(at)gmail(dot)com and I’ll send you an Excel sheet for the Anderson-Darling test and normal probability plot.Cheers, BTDT

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#148346

Member

Dear Friend,
There is many more to explore in excel.
Please try the following path & see whether it satisfy your need or not.
1. Select Tools manu -> Add-Ins.
2. One dialog box will appear with many option. Select “Analysis Toolpak”If analysis toolpak is not loaded in your system then ask administator to installed full version of MS-Office.
3. Again goto “Tools Menu” -> select “Data Analysis” option.
4. One dialog box will appear with many option. Select “Histogram” to plot histogram & ND curve for your data.
5. Just follow the instruction appear on the Screen.
Rgds,