Normal Probabilty Plot
02-02-2017, 04:32 PM
Post: #5
 KeithB Member Posts: 298 Joined: Jan 2017
RE: Normal Probabilty Plot
If anyone wants to make a Normal Probability plot with a fit:
1. Put your sorted (lowest to highest) data into a column of the Statistics 2Var App.

2. Use the make function to fill another column with the formula:
NORMALD_ICDF((X-0.5)/N))

With X going from 1 to N (The number of data points)

3. Plot your data.

4. Hit the Fit button.

Note: As Tim pointed out, there seem to be many ways to make this plot. I have also seen a slightly more complicated formula to generate the probabilities which comes from NIST's engineering statistics handbook: http://www.itl.nist.gov/div898/handbook/...rmprpl.htm

To create this alternate form:
Use the make facility to create NORMALD_ICDF((X-0.3175)/(N+0.365)) from 1 to N. In the first row insert NORMALD_ICDF(1-0.5^(1/N))
In the last row put in NORMALD_ICDF(0.5^(1/N))

Proceed as above.
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 Messages In This Thread Normal Probabilty Plot - KeithB - 02-01-2017, 05:30 PM RE: Normal Probabilty Plot - Tim Wessman - 02-01-2017, 05:53 PM RE: Normal Probabilty Plot - KeithB - 02-01-2017, 07:41 PM RE: Normal Probabilty Plot - grsbanks - 02-02-2017, 08:23 AM RE: Normal Probabilty Plot - KeithB - 02-02-2017 04:32 PM RE: Normal Probabilty Plot - mark4flies - 02-02-2017, 10:25 PM RE: Normal Probabilty Plot - mark4flies - 02-02-2017, 10:29 PM

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