Normal Probabilty Plot

[KeithB]

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.