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volker_kraft

Staff

Joined:

May 29, 2014

Assessing Normality (OPG)

Topics: Assessing normality for a continuous (quantitative) variable.

Category: Probabilities and Distributions

JMP features: Analyze > Distribution, Normal Quantile Plot.

   

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Comments
david_tucker1

I found this article easy to apply to my real life data, thank you.

mia_stephens

Glad to hear it, thanks!

nurasbani

So, we do not need to calculate the residual before the normality test.

I ask this question because I found these steps (https://scholar.vt.edu/access/content/group/43c8db00-e78f-4dcd-826c-ac236fb59e24/STAT5606/AnovaJMP.h...):

 Analyze the residuals to check the assumption of normality

  1. In the Fit Y by X platform, select JMP: Save > Save Standardized
  2. The result appears in the data table as a new column/variable labeled "Y" Standardized by "X". These are the residuals.
  3. In the data table select JMP: Analyze > Distribution
  4. In the Analyze Distribution dialog window select the residuals column/variable.
  5. Study the histogram and stem-plot for symmetry.
  6. Note the skewness under JMP: Summary Statistics.
  7. Perform a Shapiro-Wilks test for normality by selecting JMP: Continuous Fit > Normal.
  8. Under Fitted Normal select JMP: Goodness of Fit.

Btw, now it's clear for me.

Thanks