Programming the statistical procedures from SAS

Normal Probablility plot

Occasional Contributor
Posts: 6

Normal Probablility plot

Hi All,

Could you let me know if anyone avire of this concept.

in my study i have a requirement for probability plot the query is like this --> "Normal probability plot with simulation envelope from the mixed model" means i should i do?

1) is it from raw data or

2) should i consider anything from mixed model results?

thanks in advance.

Hima B

Posts: 3,839

Re: Normal Probablility plot

Normal probability plot of what? The residuals?

Many SAS procedures produce normal quantile-quantile plots automatically. The Q-Q plot is very similar to the probability plot, but the Q-Q plot is usually easier to read than the probability plot, and makes deviations from normality more apparent.

A "envelope" usually means that you run an analysis many times and look at the 2.5% and 97.5% percentiles of the results.  For a Q-Q plot, you might bootstrap the data and store the data for 1000 Q-Q plots. You then plot the appropriate percentiles as the envelope.

I do not know what the term "simulation envelope from the mixed model" means.  Perhaps someone else might be able to provide insight.

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