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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: confidence intervals histograms |

Date |
Tue, 15 Feb 2005 18:42:45 -0000 |

Histogram bars: sounds tricky. But crudely the error on any histogram bin count will scale as the square root of that count. Unfortunately, there is no -xsc(root)- option on which bars would be approximately the same size. I suggested one some time ago to StataCorp. I suspect your problem is not literally one of drawing a histogram, but just a kind of generic fat value bar + thin error bar plot. You can follow the Roger Newson route, or knit it yourself by something like . twoway bar ... || rcap ... but either way you need to have the variables to hand. A search through the archives will find this one dividing the community right down the middle. answers. Some people are happy with a fat bar + thin bar format, even if half the thin bar is hidden beneath the fat bar. In my experience it is both common and popular in various biological sciences, but less common and less popular in other fields. Others regard it as a very poor format. Stata user Paul Seed has used (and may even be responsible for) the term "detonator plot". At a London users' meeting some years ago when it was reported that some people wanted this kind of graph wired in as an official Stata command, the response from the floor was roughly "No. No. Terrible idea. Very poor". In my view, there are three main criticisms of this format: 1. The common practice of burying half an error bar obliges the conscientious reader to try to reconstruct it mentally. That is poor graphical etiquette, to make the reader guess at what would be shown if the graph had been properly prepared. (In Stata, this is avoidable so long as the fat bar has no color or the thin bar is drawn on top.) 2. There is graphical equivocation in that fat bars usually have base 0 and so often look much bigger than error bars. Whether the bar value is not 0 is, on the other hand, commonly not the scientific issue. Thus this design often puts the emphasis in the wrong place. 3. This format is often associated with a very small amount of information, and so a table would often be more informative. Naturally, * poor use does not discredit proper use * calling a graph by a derogatory name does not make it a poor kind of graph. Nick n.j.cox@durham.ac.uk Richard_Lenhardt@rush.edu > May I ask if anyone knows if there is an easy way to create > graphs with > confidence intervals displayed on top of histogram bars? * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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