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dbmurrell
Level I

Moving Box Smoother (Graph Builder)

I'm using the moving box smoother in JMP 19 graph builder and can't seem to find any definitive documentation on how to interpret the 2 shade gradations surrounding the smoother curve. Are these confidence bands? If so is the lighter (wider) the 99% band and the darker (narrower) 95%?

1 REPLY 1
XanGregg
Staff

Re: Moving Box Smoother (Graph Builder)

Moving Box is an generalization of John Tukey's "wandering schematic plot" where "schematic plot" was a name he used for the box plot. 

As I recall (I don't have his book handy), his version used 10 or so overlapping intervals and made a box plot for each interval and then connected the key values with lines.

Our generalization uses the local kernel smoother to compute moving versions of the 5 key values (lower whisker, lower quartile, median, upper quartile, and upper whisker). Except a whisker is hard to translate to a local kernel fitter, so we use 0.005 and 0.995 quantiles instead, which are about what a 1.5 IQR whisker would translate to for a Gaussian distribution.

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